By the Light of the Moon
by Ilovetoread09
Summary: When Richard Castle finds a dead body near a boat home he's renting for the summer, he triggers events that introduce him to him a world, and a woman, that are beyond anything he's ever imagined. AU
1. Chapter 1

AN: So, here's another story. Once again this is another one that's mind of out there, so bear with me if you can.

Disclaimer: I don't own Castle.

* * *

Chapter 1

Richard Castle sighs as he sits down for a late night/early morning snack, lounging on the sofa in the small boat he's occupied for the past month. He lays his legs fully on the couch, not even bothering to attempt to swing them over to the narrow space next to him between the couch and the coffee table.

As he eats, the author occasionally steadies himself as the he feels movement beneath him. He grimaces, carefully balancing his plate with one hand and his fork with the other. That's one thing he hates about living on a boat, the constant sway. He doesn't get sea sick, no. He just loathes the unbalanced feeling the rocking gives him.

He polishes off his meal and goes to to rinse the plate in the sink when he hears a thumping noise. Furrowing his eyebrows, he listens, hearing the noise again. What the hell?

He decides to investigate, opening the hatch above and stepping out onto the deck. The moonlight from the cloudless sky shines down on him, providing him with enough light to see. He stops, standing still in order to hear the direction of the noise. After a few moments, he determines it's coming from the bow. Figuring the source is probably a log, he sighs, going to the area to remove it so it doesn't disturb him for the rest of the night.

He reaches the bow, ready to grab the infernal piece of wood, when the sight in front of him makes him gasp. Okay, that is so not a log.

Instead, his eyes behold a person, or what used to be a living person. Mouth agape, eyes still open, the lifeless body stares at him, her gaze empty, cold. There's a small pool of blood flowing from her abdomen and Rick fights back a shudder at the image. He may write mystery novels for a living, but seeing a dead body is a whole different thing.

He quickly unlocks his phone and dials 911, forcing himself to look away from the deceased. The operator answers on the third ring and he takes a breath, calming himself.

"Hi, yes. I would like to report a dead body."

* * *

The police arrive about forty minutes later, sirens whirling. Rick's standing on the dock as they approach. The medical examiner had started earlier, determining the case a homicide, so the twelfth precinct was called. The first to get out of the cars is a woman, a very attractive woman Rick admits, with shoulder length brunette hair. She strides past him in power heels, clearly focused on the task at hand.

"What have we got, Lanie?" he hears her ask. He glides closer enough to eavesdrop.

"Female, twenty five, two stab wounds to the abdomen. Also, this one has a crescent moon shaped birth mark."

"Just like the others," the detective mutters in a resignated tone.

The author can't help himself as he blurts out, "Is she a victim of the Full Moon Killer?"

The detective whirls at the sound of his voice, her eyebrows raised.

"Unfortunately, most likely Mr..."

"Castle, Richard Castle. I'm the one who found the body."

"I see," she mutters, lips pursed. He gazes at her, drawn to the fire in her hazel eyes.

"This is the third time he's struck," he comments. Whoever this guy was seemed to be pretty clean in his killings. Which was interesting since the killer strikes in the dark during a full moon..

"I'm aware, Mr. Castle," she bites.

"Sorry, Detective..."

"Beckett," she finishes, her tone softening. "Sorry, I'm being unprofessional." She shakes her head. "Anyway, how did you come across the body?"

He recounts his tale to her and he notices her shoulders drop in disappointment.

"So, you didn't see anything beyond the body?"

"No," he replies, feeling slightly guilty he can't do anything more to help.

She frowns, her eyes sliding over to his boat.

"Do you mind if my fellow detectives have a look around your vessel?" she inquiries.

He gestures widely toward the boat. "Go right ahead."

She and two male detectives, Ryan and Esposito, board the boat, canvassing the area.

"How long have you owned this boat, Mr. Castle?" she asks as he follows suit.

"I actually don't own it. I'm renting it out from an elderly couple; they're in Florida right now."

"Bit small for someone of your supposed wealth, isn't it?" Detective Esposito prods. Rick rolls his eyes.

"It's research for my next book. _Storm of the Sea_." The trio glances at him and he shrugs. "It's a work in progress. I like to get the feel for things when writing and researching, so I figured why not rent a boat?"

"How long have you been here?" Detective Beckett asks as her fingers slide over the top of his coffee table.

"A month, but I'm renting it out for three. So, until the end of the summer." He smiles as the detectives continue their exploration. "Watch your head going into the bedroom," he warns as Beckett enters the room. The bedroom is a another level lower than the living room and just as small. It's big enough to fit a bed and nightstand, both of which are shoved in opposite corners of the room.

"What's this guy's motive anyway?" Rick questions, making Beckett sigh.

"I can't tell you that," she answers.

"Because you don't know or you're not allowed to?"

"Both." Her tone's frustrated as she runs a hand through her hair. "Just wish we could pin this guy down," she mutters, clearly more to herself than him. She leaves the bedroom and returns to the deck, hands on her hips as she speaks to the other two detectives. He trails after her, listening in as much as he can.

"Send some patrol boats out to see if they can find anything," she orders. She folds her arms across her chest, her annoyance rolling off in waves.

"Maybe you should try talking to Jerry McNultly, my neighbor. He's usually out on the dock late, maybe he saw something," Rick suggests, wanting to do anything to help.

Detective Beckett blinks at him, seeming surprised. "Um okay, we'll try that. Anyway, thank you for your time. If we have anymore questions, we'll contact you."

He nods as she walks off with the other two.

He stares at her for a moment , finding himself intrigued by the brunette. He's not sure why, but she draws him in, and he knows that there's a story behind her eyes. He wants to, no, needs to know it.

It gets him thinking; perhaps he should pay a visit to Mr. McNulty.

After all, he would do anything to help the NYPD.


	2. Chapter 2

AN: So, here's the next one. Thank you for all the follows, reviews, and favorites for this story so far. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 2

Mr. McNulty is an elderly man in his late 70s. When Rick pays him a visit, the elder man is preparing a pot of tea for himself in the small kitchen of his boat.

Rick knocks on the door frame, grinning as Mr. McNulty turns around, giving the author a wave.

"Hey, Rick," he greets, walking over to the table. "What brings you 'round here?" He smiles kindly, gesturing for the author to sit at the table.

"I'm actually here about something that happened last night," Rick starts, placing himself in a chair across from the man.

"The body you found, right? Must've been quite a sight," the former sailor remarks.

"Yeah, that," Rick murmurs. "News travels fast." He hadn't told anyone about finding the body, not wanting to scare the residents. Looks like he didn't need to.

"Well, when the cops show up in the middle of the night, people are going to take interest." He chuckles before his expression sobers. "But what does that have to do with me?"

The younger man shifts in his shift. "I know you're usually out during that time of night."

McNulty nods. "Yep, insomnia can be a monster. One of the many souvenirs I took from my career as a sailor."

"Yeah, so I was wondering if you saw anything out of the ordinary?"

The man sighs, placing his tea cup on the wooden surface. "Unfortunately, no. Trust me, I would've noticed if someone took a boat out in the middle of night."

The author frowns, looking around the interior of the boat. Various marine decor is scattered on the walls, a combination of souvenirs from long ago and more current stereotypical decorations.

"I see," Rick remarks, his eyes roaming over a ship in the bottle that's occupying space on an upper shelf.

"However, I do have my theory of what's going on."

"Oh?" Rick raises an eyebrow. "What do you think is going on, Mr. McNulty?"

"Call me Patrick, please," the old man insists. "And what I think is happening is whoever this person is has been taking these woman out in a boat into the middle of the ocean, or at least far enough away from shore. Then, he kills them and dumps their body, leaving it to wash up on shore."

Rick purses his lips, scrunching his eyebrows "Do you know why?"

The former sailor lifts his shoulders. "Beats me. I really do hope they catch this guy, though. It's so sad, to think of what those families must be going through right now."

Rick concedes as he examines the bookshelf next to him. "I see you have a lot of nautical and oceanography books." He stands up, his fingers skimming the spines, some of the titles piquing his interest.

"You can take the sailor out of the sea, but you can't take the sea out of the sailor. I keep those as memorabilia of the good old days. Also, my grandkids love looking at the pictures. This one is their favorite."

Getting up from his chair, Patrick selects a book from the shelf. As he does so, Rick notes the star-shaped ink on the sailor's left hand.

Noticing, Patrick chuckles. "North Star," he explains. "It's an old sailor superstition that it helps us find our way home." Flipping through the book, he smiles. "This is just a book on mythical sea creatures. It's an adult version, so I water it down for the kids. They beg me to read it anytime they visit."

Rick takes the book from the old man, skimming it in fascination. Mythical creatures have always been an interest of his. Perhaps he could learn even more about the potential beings that evade the human population.

"May I borrow this?" he asks.

"Sure." Patrick grins in amusement as Rick continues to examine the book.

As he does so, there's on knock on the doorframe. Rick looks up, beaming when he sees who it is.

"Oh, hello Detective Beckett," he greets. She nods in acknowledgement before turning to Patrick.

"Hello, Mr. McNulty," she says, stepping into the space. "I'm Detective Kate Beckett. I just have some questions for you regarding last night."

Rick waves his hand dismissively. "No need, Detective. I already asked him, but he doesn't know anything."

She raises an eyebrow skeptically. "Oh?"

"Yes, I'm afraid Rick is correct. Though, I did tell him my theory." He recounts his idea to the detective and Rick sees her lips purse, head nodding in agreement.

"We figured as much. Unfortunately, we've come up empty in our search on the river."

'Maybe the guy doesn't ditch the boat? The killer could just return the boat to a secluded area and clean it up," Rick suggests.

"Mmm," Kate responds. Turning to the elderly man, she says, "I'm sorry for bothering you, Mr. McNulty. However, if you do find anything, you can let us know." She hands him her card before turning back to Rick. "Can I speak to you outside?"

He follows, finding himself admiring the way she walks with confidence, power. He likes that in women. It also doesn't hurt that she's very attractive, with her hazel eyes, heart shaped-face and great-

"What do you think you're doing?" she asks, interrupting his ogling. She's glaring as her nostrils flare. He can't help but find it kind of adorable.

"I'm sorry?" he replies, tone confused.

"This is an NYPD investigation. We don't need civilians butting in on such a pernicious case."

"Oh, good vocabulary word!" He actually finds it hot she can use such a word.

"Focus, Mr. Castle," she snaps. "You can't be interfering with my case. Got it?"

"Yes," he mumbles, pouting. There's a part of him that feels obligated, however, since he did find the body. "Maybe I can consult…"

She shakes her head. "No, absolutely not. The media has been all over my team regarding this case, particularly in the last few hours. Bringing a civilian in to help would not be a good idea."

He sighs, understanding her thought process. "Okay, okay. I'll stop investigating, I promise."

"Good," she says, turning to leave. She stops, eyeing him. "Oh and if you do, you'll find yourself in handcuffs."

"I actually wouldn't mind if you handcuffed me, Detective." He winks. She snorts and rolls her eyes.

"In your dreams, Mr. Castle. Good day." With that she leaves as he stares after her.

He scowls slightly. She is frustrating but intriguing nonetheless. She's a challenge, something he's never had before now. Normally, women throw themselves at him, but not her. She doesn't seem like the type anyway. He realizes he likes that, along with her determination and the story behind her eyes. There's something there and he wants to know her history, of why she's a cop, of why there's a certain darkness and sadness clouding her irises.

Shaking his head, he plays with the book in his hands, admiring some of the pictures as he flips through it. He'll have to settle for the origin stories of mythical creatures.

For now.


	3. Chapter 3

AN: So, here's the next one! Thank for all the follows, favorites, and reviews for this story!

Disclaimer: I don't own Castle.

* * *

Chapter 3

Rick hums to himself, scribbling notes down. The scent of the sea hits his nose and he smiles, enjoying the breeze. Looking up, he observes a fisherman reeling in his line, his expression ecstatic as a fish flip flops on the hook.

Rick sighs, steadying himself as the boat beneath him rocks as he moves to the front. Gazing out, he grins as he sees various people out own their own boats, either fishing or sightseeing. As for him, he's just observing the people, trying to pinpoint the behaviors of fishermen and the like for his next Derrick Storm book. So far, it's somewhat interesting, but mostly boring.

As he spots a couple getting quite busy on a sailboat, the sound of an approaching motor boat reaches his ears. He turns, noticing the NYPD logo on the vessel. He also recognizes the two people manning the boat.

"Hello, Detective Ryan and Detective Esposito," he greets kindly.

The two shoot each other a look before glancing at him.

"Hey, Mr. Castle," Detective Ryan greets. The other detective just nods, his face stoic.

"What brings you out here?" Rick asks.

"We're trying to find any possible dumping spots," Ryan states, earning an elbow from Esposito. "What?"

"Where's Detective Beckett?" Rick asks. He's eager to see the beautiful brunette, perhaps even get on her good side.

"Not here," Esposito answers curtly.

Rick pouts, not caring if the detectives laugh at him. He is really hoping she'd come along. Maybe he could invite her out for a boat ride, just the two of them…

"Oh, and don't bother trying to get her out here with you," the shorter detective says, noticing Rick's contemplative expression. "She's got a bit of an aversion to water."

"Dude," Esposito hisses. "Beckett will kill you if she finds out you told him that."

"Don't worry, boys," Castle chirps. "I won't tell her you said anything."

"Right," Esposito mutters. "Anyway, we need to get going. This spot is too close to shore according what the medical examiner said."

"See ya around, Mr. Castle," Ryan says before the two speed out further into the water.

Rick chuckles, sure he'll see the detectives again. While he doesn't want to get arrested, doing bit of independent investigating wouldn't hurt. After all, he needs to know the story and maybe even help find closure for the two victims' families. With that thought, Rick starts the boat, heading toward the docks.

Time to do some research.

* * *

He pours over articles, finding anything he can about the killings that he hasn't heard before from the media. Unfortunately, there isn't much. Most of it's the same information regarding the birthmarks, the genders, age, and the way they died. He does find some conspiracy theories, but they're too outlandish, even for him.

Scowling, he closes the laptop, giving up for the moment. He really wants to help, but it looks like that'll be near impossible unless he has access to NYPD files, which he knows will never happen.

Pushing the chair back, he gets up, going to get some dinner. As he raids the fridge, his phone rings. Looking at the caller I.D., he beams.

"Hey Pumpkin," he greets, grabbing a packet of cheese off the shelf. He and Alexis speak every night before she goes to bed. She usually calls first, wanting to check in on him, always playing the parent.

"Hey Dad," his daughter replies, just as cheerful. "How's the book coming?"

"Great," he lies. He hears a sigh from the other end of line. "Hey, I'm working on it. Research just takes a while, you know? There's so much about life at sea I didn't know."

"Everything you've observed so far is boring, isn't it?" she asks in a deadpan tone. Ah, his daughter knows him so well.

"Pretty much." He shakes his head. "I might've been better to actually go out on a real sailing trip inside of renting here at the dock."

"What about the dead body you found? Surely you've thought of something from that."

"Ehh, not too much,." He's been inspired a bit. However, the limited information he had seen didn't allow him to expand his mind all that much.

"That's a shame," she remarks.

"Did you do anything fun today?" he asks, dying for a change in topic. Focusing on his writing drought depresses him to no end.

"I mainly just hung out with Paige," she answers. "Really, like I said last night, the Hamptons is the same old thing. You're really not missing much."

"Mmm," he hums. She's probably right. If he were to go out to his Hamptons home this year, it would be the same parties, the same people, the same gossip. It's nice having different surroundings, different people who are more down to earth. Particularly a certain detective…

"So, you want to read another one of those passages?" she questions.

Ah, yes. Ever since he'd informed her about his newest possession, he has played a guessing game with Alexis where he recites part of a passage from the book and she must figure out which mythical creature it could be. So far, they've had Nessie and Beist Kione. He grabs the book from the desk and flips open to the next one.

"Ready?" he inquiries, eager.

"Yep," she responds, her tone matching his.

"Okay," he says, clearing his throat dramatically before continuing, his eyes scanning the words, trying to avoid the more obvious clues. "This creature has supposedly existed for over a thousand years, and sailors have spotted it in different parts of the globe."

"That's like every mythical sea creature," Alexis snorts.

"Wait," he interrupts. "This creature bears a crescent moon shaped birth mark and is said to use water to heal other sea creatures as well as humans. The status of its mortality has always been questioned. However, some believe that it gains its power and possible immortality from a full moon. It is also rumored that the immortality can be transferred to a human. However, the price of the transfer is fatal to the creature…" he trails off, his mind spinning at the words in front of him.

"Dad?" Alexis quizzes, concerned.

"Um, listen Pumpkin, something came up. I'll call you back in a bit." He promptly hangs up and grabs his shoes.

Looks like it's time to visit the Twelfth Precinct.

* * *

About a half hour later, he steps onto the Homicide floor of the precinct. He glances around, noting that most of the officers are packing up to go home. However, unsurprisingly, a certain female detective is still sitting at her desk with no signs of leaving any time soon.

He walks up to her desk, grinning.

"Hello, Detective Beckett," he says. She pops her head up, furrowing her eyebrows in confusion.

"Is there something I can do for you, Mr. Castle?" Her tone indicates that she hopes not.

"I think I may have found the motive for our killer," he announces.

"Our killer?" she nearly growls.

Undeterred, he continues, "Yes, read this." He hands her the book, opening to the section.

She raises her eyebrows, a playful smile forming on her lips. "You think our killer is looking for an Afanc, which consists of a crocodile, beaver, and possibly a dwarf? I don't think either of those women looked like that."

"Oh, whoops." He flips to the real section and she begins to read. As she does so, the amusement vanishes, astonishment replacing it.

"It's possible," she starts. "But I highly doubt…"

"Look, when I visited Mr. McNulty, he had his own superstition about finding his way home, hence his tattoo. It's likely that there are other sailors and/or fishermen have their own superstitions, or even believe these creatures exists. I'm not saying the creatures are real, but the killer thinks they are. He or she must want immortality, hence the killings."

"Not like they would get it," she grumbles. "Who the hell wants to live forever?"

"Well, wouldn't you want unlimited time?" he asks. The idea of immortality is awesome. The ability to live forever and do whatever you want? He wouldn't say no if someone were to offer him the opportunity.

"No, because then you end up alone and bored, probably," she answers. "I'd rather not mess with the cycle of life."

He pouts. "You're no fun."

"Yeah, well, some of us have to be kill joys," she responds with a roll of her eyes. "However, I do thank you. We'll look into this, although I doubt anyone willing admits to believing in any type of mythical creature."

"Hey, from what I've seen from my book research, you'd be surprised." People would believe in anything from vampires to stranger creatures. He believes in some of them, but not all.

"Mhmm," she replies, eyes scanning over a document, obviously wanting him to leave.

"Hey, listen," he starts. "It's getting late and something tells me you haven't eaten much." He eyes the thrown aside chip bag.

"I actually had Chinese food earlier. This was just a snack," she interjects, scowling. It's cute.

"Right," he says. "Anyway, I'm sure you're hungry by now and I know this nice little hole wall that has great burgers…"

"Remy's?" she assumes, her irises brightening.

"Yes, that's the one!" He smiles, glad to see they enjoy at least one thing in common. He's sure if he digs deeper that there's more.

"Their strawberry shakes are delicious," she states. Then, rolling her eyes she says, "However, if this is your way of asking me out on a date, then I must decline."

He shoots her puppy-eyed look, the one no one can resist. "Come on, it'll be my treat. Think of it as my way for making up for annoying you." He flashes her one of his charming smiles, but as he suspects, she isn't moved.

"You'd have to order me the whole menu to make up for past and future annoyances."

"Future annoyances?" he asks, hopeful. Oh he so won't mind if she lets him see her after this.

"Something tells me I'll be talking to you often, whether I like it or not." Her expression is half full amused, so perhaps she doesn't hate him completely. "So, come on, let's go." She picks up her jacket, swinging it over her shoulder. He follows, keeping in step with her. When they enter the elevator, he catches a whiff of her perfume. Fruity, but pleasant. Mmmm.

"So, strawberry milkshake?" he teases.

"What? A girl can't enjoy a milkshake?"

"No," he says, realizing his mistake. "Just that-"

"You think I'm too much of a hardass to like milkshakes, particularly fruit flavored ones?" He has the decency to look sheepish. "Just for that, I'm stealing your fries, so be prepared to double that order." She smirks, winking.

"Got it," he mumbles. Inside, he's jumping for joy. She appears a little more open. Maybe dinner will aid in that.

"Good," she remarks, stepping out of the lift. "Because I don't like to share." She turns to face him, a mischievous glint in her eyes.

He's dumbstruck for a moment before following, playfully leering at her.

"Neither do I, Detective," he murmurs. "Neither do I."


	4. Chapter 4

AN: So, here's the next chapter! Thanks for all the follows, favorites, and reviews for this story! I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 4

Within the next half-hour, the duo is seated at one of the booths of the small establishment. It's cozy, and the place where Rick likes to go when he's grown tired of eating at home or dinners at a fancy restaurant. Also, he's treated like a regular person here, which he doesn't mind one bit.

Currently, he's watching the woman across from him demolish her fries while dipping them in her strawberry milkshake.

"How is that appetizing?" he asks, his face twisting in disgust.

"It's delicious," she hums, grabbing her last fry, dipping it, and popping it in her mouth. "Don't judge, I'm sure you have some weird food favorites." She smirks, her eyes teasing.

He huffs. "I do not, despite what my mother and daughter think. Potato chip ice cream is the absolute best flavor ever!"

The detective's expression morphs into one of aversion. "No thanks. I like the traditional flavored ice cream just fine."

"Don't knock it until you try it," he responds, polishing off his cheeseburger. "Anyway, what do you think of my theory?"

She shrugs. "I mean, like I said, it's possible. However, I think it's a long shot that anyone actually believes those creatures exist."

"But do you think it has merit?" He grins triumphantly.

She rolls her eyes. "Yes, I do think it has merit. However, finding someone to openly admit it would be hard."

"Not necessarily," Rick comments, taking a swig of his soda. She raises an eyebrow. "Think of how many people believe that Big Foot exists or even those that believe in the Loch Ness monster. The real fanatics are extremely vocal about expressing their theories. Who's to say this is any different?"

"Maybe, but this person is killing innocent women. It's unlikely that the killer would be vocal about such a dead giveaway."

"Or, the killer could use it to his or her advantage. After all, aren't most crazy theorists seen as harmless?"

She sighs, sitting back. "True." She purses her lips. "I'll have my team look into it. However, that means we're going to have to re interview that whole dock area."

He can see that the prospect of the activity doesn't exactly thrill her, but it doesn't pain her either.

"I can help, if you want. I've been there long enough that most of the people trust me." Most of the population on the boat basin is friendly to him. He hasn't had any run-ins and perhaps his charming personality would make people let their guard down. "They might be more comfortable talking to the average citizen than a detective."

"You're an average citizen?" she teases.

"Well, someone who doesn't have a badge," he supplies. "Besides, I'm writing a book, so I have a perfect excuse."

She groans, seeming to agree with him. He forces himself to hold back the victorious grin that threatens to form. "Fine, fine. You can help. However, if I catch a whiff of trouble from you or because of you, you're going in handcuffs, understood?"

"I wouldn't mind that," he murmurs, leering.

"I'm serious, Castle. I don't need any more problems than I've already got from this case." She closes her eyes, two fingers massaging her temple. "The media is hounding us, of course, and now the mayor's starting to circle since this affects both the marine community and the every day citizen."

He frowns, hating to see how much stress Beckett is under, despite her and her team doing all they can to catch whoever it is committing these crimes.

"I can ask the mayor to back off," he offers.

"You?" She appears to be containing a snicker.

"I'm close friends with him. We're poker buddies, actually. I can just suggest that he calm down bit."

"Thanks, but no thanks. I know what I signed up for when I took this job. We need to work faster, that's all."

He nods, still contemplating on calling his long time friend within the next day or so. Just to give the NYPD some breathing space.

He waves the waitress over for the check and begins to pulls out his wallet.

"Hey, we can split this," Beckett interjects, reaching into her purse.

He shakes his head. "Nope, this is my treat. Making up for past and future annoyances, remember?"

She slouches against the seat, pouting. However, Rick can see the small smile she's fighting. He doubts she gives up that easily, she's only letting him have this one.

Once the check is taken care of, the duo departs, heading out the door.

"Well, it was nice talking to you, Detective," he says. "We should do this more often."

"Don't get your hopes up," she replies in a playful tone. "But yes, this was…nice."

He rolls his eyes. Stubborn woman.

They part ways and he thinks about the case and her, but mainly her. How her eyes sparkle when she teases him, the way her smile lights up her face. And oh, those cheekbones!

He surprises himself, not usually one to become smitten so quickly. He knows it's only lust with her and nothing more, but he does find her very interesting and that there's a story behind those gorgeous hazel eyes.

Maybe he can learn more about her in the coming days.

* * *

Over the next few days, Rick gains a new respect for the NYPD as he questions people around the boat basin. Yes, he's interviewed people for his books before, but not when there's a murderer on the loose and everyone is high-strung.

Most answer his questions with minimal response, and when they do, their tone is terse, suspicious. The only ones who seem slightly more relaxed are the older citizens, and even they don't have much to offer him.

He knows the next full moon won't be for a while. Regardless, he thinks it would beneficial to prepare and perhaps try to go out to the water the night of the full moon. With Beckett, of course.

After another day of questioning, Rick lounges on the couch in the boat. Taking out his cellphone, he dials a familiar number.

"Hey, Big Cheese," he greets jovially.

"Hey, Rick," the mayor replies, chuckling. "How are you? I heard it was your boat that the newest victim wound up near. I'm terribly sorry to hear that."

"Eh, it makes things interesting," the author remarks. "Anyway, that's why I'm calling actually."

"Oh?"

"Yeah, I want to talk to you about the NYPD Homicide team that's investigating the case."

"Is everything okay? I thought you were cleared as a suspect?"

"I was," Rick hesitates, carefully choosing his next words. "I've talked to the team members of the Twelfth Precinct a few times, particularly the lead detective. I'm under the impression they're feeling a… little overwhelmed."

"Well, they are investigating a murder, Rick," the mayor reminds him. "It's their job."

"I know, I know." Rick purses his lips, sitting up straighter. "It's just that I have a feeling the investigation would go a little smoother if people weren't on such high alert. The team is a hard working group of detectives, would it really be that bad to give them some leeway?" His tone is convincing and Rick can practically feel his long time friend conceding.

"I'll see if I can get the media to back off a bit, and I will give them a little more time before checking in on them again."

The author breathes a sigh of relief. "Thanks. I would appreciate it and I'm sure they will too."

"Okay, Rick, I'll see you at the next game," the man says before hanging up.

His main goal complete, Rick opens his wallet. He removes a certain business card and stares at the number for a few moments before putting it away. What he wants to tell Detective Beckett could be accomplished in a phone call.

However, seeing her in person is so much better.

* * *

He arrives at the twelfth precinct the next morning, a pastry in hand. He would bring her coffee, but something tells him she's very particular about what she drinks.

"Good morning, Detective," he greets once he's close enough to her desk.

"Morning, Castle. What brings you here?" she asks.

"I just wanted to give you an update on what I've discovered," he states, setting the bear claw down on her desk.

"Oh? You could've picked up the phone and done that." She raises an eyebrow, a knowing look in her eyes.

"Yes, perhaps I could've, but then I wouldn't be able to see your lovely face."

She blushes, but rolls her eyes. "So, what have you found out?"

"Nothing, unfortunately. Everyone's pretty tight lipped."

"Told you so," she remarks. "Who would openly admit to believing in mermaids?"

"I'm sure someone will, we just have to find them." He shrugs, realizing that this is the first time they've openly mentioned the type of creature.

"Right," she replies, her tone skeptical.

"Perhaps we could plan out our next move at lunch again? Maybe somewhere a little nicer?" He gives her one of his boyish smiles. She's not impressed.

"While I thank you for your help, Castle, we can take it from here," she replies, her voice stern.

He blinks, his mind a mix of bewilderment and hurt by her change in attitude. What the hell?

"Okay, no lunch then. Dinner maybe? Or we can just discuss it on my boat," he offers.

She shakes her head. "While I thank you for your input, it is not a good idea for a civilian to be on such a dangerous case."

He frowns. Her voice is like steel, unwavering. However, her eyes tell a different story. He sees resolve in them, but also sadness, or despair? He's unable to tell which.

"Is something wrong?" he inquiries.

She bites her lip. "Again, I thank you for your help, Mr. Castle." Mr. Castle? Ouch. "However, we do have work to do, so if you don't mind…"

He sighs. "I'll see myself out."

He walks to the elevator and enters. Right before the doors close, his gaze lands on her desk again and he finds her staring at him, a look of melancholy on her face. However, as soon as she notices him, it disappears in a flash.

He furrows his eyebrows in confusion. What's going on with her?

Whatever it is, he plans to find out.


	5. Chapter 5

AN: Thanks for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 5

Rick spends the next week attempting to learn more about marine life like he had been doing previously. Unfortunately, nothing seems to inspire him when it comes writing. However, there is a story nagging at him. One that involves a sassy, sexy, hazel-eyed detective.

There are some nights where he sits on the dock or lounges on the upper deck of his boat. During these moments, he gets the sense that he's being watched. However, the feeling only lasts about a minute before it vanishes. Whenever the sensation does occur, he looks around on the both the pier and the water, only to find himself alone. He shakes it off most of the time, figuring he's being paranoid due to his investigating. However, the thought of someone watching him still makes him a bit nervous.

When he reaches the weekend, Rick plans to go out on the water again, in hopes of finding something interesting. The real gift, at least to him, however, comes as he is preparing the small vessel. He just finishes ensuring that there is enough gas in the tank when he hears the click of heels behind him. He turns, his eyes brightening by the sight of none other than Detective Beckett.

"Hello, Detective," he greets. "Do you have questions for me?" He figures that why she's here, anyway.

The brunette teeters on her heels, looking unsure of herself.

"No, I'm not," she replies, biting her lip. "I came to…apologize for a few days ago. I was rude to you and shouldn't have been. I'm sorry." She smiles. "And also, thank you." He gazes at her confusion. "The press has been surprisingly quiet lately and the mayor's stopped circling. I don't know what you said to him, but thank you. It lets us continue our investigation a little easier."

"It's no problem," he replies, waving a dismissive hand. "So, is that all you came for or…"

"I actually wanted to ask if you would like to consult on the case, since you're into mythical creatures and all that and you do have experience in the field due to your research." She tosses him teasing look, causing him to chuckle. "My captain is okay with it."

"I would be more than happy to," he says. "Do you need me there bright and early?"

"If you could." She shrugs.

"Okay then, I'll see you Monday? "

She nods. "See you then, Castle."

He beams at her as she walks away, every part of his body overjoyed that she's reverted to using his last name again. It makes him feel more cop-like. He briefly contemplates telling her his idea to help with the case, but decides against it. No need to start throwing out ideas right away. He figures the precinct is a better setting for that.

Hopefully she'll agree to his idea.

* * *

He arrives bright and early Monday morning, bear claw in hand. Beckett seemed to have enjoyed it the last time he was there, so hopefully she likes it this time.

"Morning, Beckett," he greets, placing the pastry on her desk. He spots a coffee cup on her desk already. Probably from the precinct, no doubt.

"Morning Castle," she replies, giving him a small smile, her eyes showing gratitude as she grasps the treat.

"So, I had an idea,"

"Already?" she jokes.

"Well, I've had it for a while now." He hesitates. "The full moon is next week and I have a boat. I was thinking maybe we could go out and try to catch the guy in the act?"

She frowns. "We don't know how far out he or she goes. Plus, it would be dangerous to travel in the dark."

He purses his lips, surprised she would let a little thing like nighttime stop her, she doesn't seem like the type. He then recalls what Detective Ryan told him a couple of weeks ago.

"My boat is perfectly safe, it has life vest and everything," he states, raising a knowing eyebrow. "I promise not to let you fall in."

"That's not what I'm concerned about," she mutters, seemingly to herself. "I'll mull it over and let you know what I decide though, okay?"

He nods, and sits down in the chair next to her.

A few moments later, she hands him a stack of case files. He combs through them, unable to find anything that connects the victims. He does find it interesting, however, that all three victims' search history was erased on their browsers the night before their deaths. Unfortunately, police notes indicate that nothing of concern was found during the recovery of said history.

Both he and Beckett spend another few hours going over files, since she doesn't have anything else on her plate. Their silence is comfortable, easy, the two exchanging only a few words back and forth. He finds that he enjoys it immensely. However, evening comes and nothing turns up and Rick finds himself saying goodbye to her sooner than he'd like.

"Want to grab some dinner?" he offers, giving her a small smile.

"Um, no, thanks, I'll pass for tonight. I'm kind of beat, actually," she admits, donning her jacket. "Goodnight, Castle."

He nods. "Until tomorrow, Beckett."

They walk out together and start to go their separate ways when reaching the street.

As she strides away, he can't help but stare at her, his eyes trailing after her. The increased sway in her hips tells him she knows his eyes are on her. He chuckles.

He's certain he's met his match.

* * *

The rest of the week is filled with browsing through case files and searching for connections. He and Beckett go out to lunch and chat, slowly getting to know each other. In fact, Rick is sure that she trusts him enough at this point to go out on his boat with him.

Beckett finally gives him her decision in regard to the search the day before the full moon is supposed to occur. She agrees, with some stipulations, of course.

"We can't stay out too late. The latest we can stay out is midnight," she says over lunch, which consists of a club sandwhich and water from a little café on the corner. "And, we need to be careful. Waters can get dangerous after dark."

"Got it," he responds. "So, we'll meet up at my boat tomorrow evening?"

She nods in agreement before getting up with him and returning to the precinct.

The next evening, she arrives at his boat at precisely eight o'clock, wearing a loose fitting white t-shirt and jeans, with comfortable looking sneakers.

"Good evening, Detective," he greets as she approaches the small speedboat.

"Hey, Castle. You all set?"

"Yep. This baby has a full tank of gas, two life vests, a life preserver, and two flashlights. We're all set."

She grins at him, albeit uneasily. Despite her trust in him, Rick can tell she's still unsure about the water. However, she's comfortable enough to go into the boat with him, at least.

She gingerly steps into the vessel and immediately sits down once she's in. He follows suit, revving up the boat and beginning to drive out into the water.

"So, if you don't mind me asking, how come you're afraid of the water?" he asks, sending her a side glance.

"I'm not afraid of it, just not… sure of it, that's all," she mumbles.

"You, not sure of something?" He scoffs.

She shrugs. "Just a quirk of mine. Kind of started when my mom died, really." She looks straight ahead, expression unmoving.

Ah, yes. During one of their lunches, Beckett admitted to him the reason for her becoming a cop. Her mother, stabbed to death and left in an alley like trash. It hurts him to see the detective so broken. However, he wasn't sure what it had to do with the water, but he wasn't going to push it.

"So, how long are you planning on renting the boat?" she inquires, moving on.

"Probably another month, until the couple comes back," he answers. He hasn't really gotten any writing done, so he may just finish up within the next month.

"Mmm," she mutters. "Then you'll return to your cosy apartment in Soho?" She smirks, giving him a wink.

"Yes, my lovely, spacious…Hey, wait a minute, I never told you I lived in Soho." He raises an eyebrow. He's talked about his home life, sure, but he never said where he lived in New York. "Abusing police power, are we, Detective?"

"A quick background check never hurt." She snickers. "And by the way, nice way to ride a horse."

"It was spring," he counters with a huff. They both laugh before going quiet, traveling for a while, the soft hum of the motorboat filling the silence.

The water is beautiful at night, particularly at sunset. Some boats are still out, but most are returning to the docks for the night. It's still fairly early for some boats to be returning, so Rick figures that part of it is because people are on high alert with the killer, tonight in particular. He hopes it isn't like this for much longer.

A while later, Beckett is the one to break the silence.

"I have to ask, how come you believe in mermaids?" she gazes at him, eyes glistening with mischief.

He cocks his head, thinking. "I like to believe that the impossible exists, I guess. The idea of other worlds or other creatures has always appealed to me." He's never been one to doubt the existence of mythical creatures. The thought of hidden species has always made the world more fun and mysterious to him. "Why don't you believe in mermaids?"

"Because there's no proof that they exist."

He chuckles. Good old cop instincts.

"A lack of evidence does not mean a lack of existence, Ms. Pre-law," he jokes. She rolls her eyes, grabbing her flashlight. It's growing dark, and while they need to be inconspicuous, riding a boat in pitch black isn't exactly the best idea. Thankfully, the full moon does provide some light.

They travel a distance in silence, scanning the area for out of place boats. The hum of the boat is soft enough that no one will hear them approach. Unfortunately, it's also lulling him to sleep.

He begins to doze off and feels, or rather hears, Beckett step over him to take control of the vessel. However, he's broken out of his drowsy state by a loud splash a decent distance away.

"What the hell was that?" she asks. He feels Beckett speed the boat up, going in the direction of the noise. He sits up, gripping his flashlight. As they get closer, he can see a figure floating along on the surface.

"Shit," they swear in unison.

He waves his flashlight around, looking for another boat. Strangely enough, he can't find any sign of one. However, his turns his attention to the woman gasping for air.

"Castle, give me a hand," Beckett says.

They jump into action, both grabbing the blonde woman and hoisting her into the boat. Blood flows from her abdomen, her skin losing coloring quickly.

"She's losing blood!" Rick exclaims, searching for something to put pressure on the wound. Beckett's already on her cellphone, dialing 911 and telling dispatch to meet them at the docks at the 79th Street Boat Basin. "Beckett, do you have anything to stop the bleeding? I don't think she's going to make it!"

The brunette shoots a look at the woman and grits her teeth.

"Dammit, you're right." She shuts her eyes, rubbing her temple with her fingers, signs of intense thinking. She opens her eyes again, and peers down at the victim. "Should I?" she mutters.

Rick stares at her in confusion as resolve fills her hazel eyes as she nods to herself.

"Castle, I need you to do me a favor and look away," she asks, voice terse.

"Why?"

"Just do it!" she snaps.

He huffs, turning away. The sound of water splashing along with Beckett muttering 'please work' multiple times under her breath, which can he just about hear over the woman's gasps, reaches his ears. A moment later the noise stops.

"You can look now, Castle," the detective murmurs. He turns back around, only to be stunned by the sight in front of him.

The bleeding from the woman's abdomen has stopped; in fact, there's no wound to be found. She's no longer gasping, but breathing normally. However, the pallor tone of her skin is still present.

"She's still needs medical attention for blood loss," Beckett states.

"How did you…"

"Docks, Castle, now." Her tone grows softer. "I can't tell you, not yet."

He shakes his head in affirmation, although his body is buzzing with curiosity.

As they ride to the docks, the sight of police lights becomes visible. Once the boat pulls up, the EMTs run to them and take the woman out of the boat, placing her on a gurney and into an ambulance.

"So…" he starts, unsure of what to say, a rare occurrence for him.

"Let's go give our statements," she says. "We'll talk later, okay?"

He smiles, gesturing for her to go ahead. He goes to an officer to give his own statement, but he's not really registering what's coming out of his mouth. He's more focused on Beckett and what just transpired.

What is going on?


	6. Chapter 6

AN: So here's the next one! Thank you for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Rick bounces on his toes as he waits for Beckett to finish talking with her two colleagues. It's about two hours after the incident and Rick and Beckett have been loitering around the hospital. After giving their statements, the duo had gone to the hospital, only to be told by a doctor that it would take a while for the latest victim to wake up. Unfortunately, there is little they can do at this point.

"So, what did they say?" Rick inquires as Beckett approaches.

"Basically just to hang back. Our statements are in and a patrol team will be sent out into the water tomorrow to see if they can find anything near the spot where we were."

He nods, holding back the question that's attempting to force itself off the tip of his tongue.

They enter the elevator, both of them silent as the day's events hang in the air.

"So, what did you say in your statement?" she inquires casually, but her tense posture portrays otherwise. Huh. He had figured he'd have to broach the topic first.

"I told Detective Ryan that my partner has magical powers, which is why our victim doesn't have any stab wounds." He can practically feel her glare burning holes in the side of his head. Rolling his eyes, he replies,"I'm joking, of course. I said we probably scared the guy off before he could kill her."

From his peripheral vision, he notices her shoulders relax.

"I can't believe I did that," she mutters. "I'm going to get into so much trouble." Her fingers rub her temple, exhaustion and worry clear on her face.

"You just saved a woman's life. I'm sure that's worth whatever repercussions there are for...whatever it is you did."

She purses her lips. "It's not going to be seen that way." Closing her eyes, she sighs, trying to decide what to do, it seems. "Look, this isn't the right place to have this conversation. Let's go back to my apartment and continue this, okay?"

"Alright." He stays quiet, knowing that her entrusting him with this secret is a huge deal. "Chinese fine with you?"

She smiles, gratitude in her hazel eyes. "Yeah, that's good."

He keeps quiet, hoping to keep her at ease, not wanting her to become skittish and clam up at the last minute. Regardless of what she tells him, he plans on staying around.

After all, that's what partners are for.

* * *

Once they're settled into her apartment and digging into cartons of takeout, the opportunity arises for the conversation. However, it appears Beckett's usual gumption is evading her. He gives her a moment, scanning her fairly spacious apartment. It's quite nice and filled with things that are definitely Beckett-flavored.

"I'm not going to judge," he promises.

"I know that, sort of," she grumbles. "I've just never shared this with anyone." The tips of her fingers graze the ring hanging from the chain around her neck. "Mom always told me it would be easy to talk about my...quirks once I found someone I trusted. I'm still not sure if what she said is true." She shoots him an apologetic smile and he shrugs.

"So, uh, what is this healing thing that you do?" he begins cautiously, but his curiosity is starting to win over.

Placing her carton down on the coffee table, she grabs a cup of water resting on a coaster. Then, she grabs a needle from an end table.

"It's better if I show you," she says. "Now, hold out your hand."

His eyes narrow, his expression wary. "Are you going to stab me with that needle?"

"It won't work on me, so I need someone else. And since you're the only one here..."

He pouts, but relents, holding out his hand. She takes it and that's when he feels it, a shock, or maybe more of a buzz, that runs from his fingertips to the rest of his body. The feeling is surprising, but not unpleasant. From the way her cheeks redden and her eyes widen, he knows Beckett feels it too. Instead of commenting, though, she pricks his finger, and blood begins to seep from the tip.

"Ouch!"

"Baby," she teases.

Taking the glass of water, she waves her fingers over it. As she does so, the water begins to float out of the glass and onto the puncture. The liquid dances around the wound before forming a circle on top of it. A soft glow emanates from the water as Beckett mutters some type of enchantment, her expression set in deep concentration. Soon, the bleeding from the needle prick stops and the wound closes up. When she finishes, Castle holds up his hand, inspecting his skin, mystified. His thoughts are a mixture of disbelief and delight when his finger appears to be blemish free.

"I can only do small wounds or shallow ones," she explains. "I've never really practiced enough to do more severe injuries. Tonight's outcome was just a stroke of luck."

He hums. "What did you mean by you're going to get into trouble?"

"You weren't supposed to see me use my powers, according to the people who set rules for, ah, people like me."

People like her? What does she mean by that? He wants to press, but her expression tells him she'd rather him do the opposite, which is fine by him. She's already revealed a lot for one evening.

"Well, your secret's safe with me," he assures her, giving her a gentle smile.

"I know, but they won't believe that."

He covers her hand, giving it a slight squeeze. He doesn't comment, since he doesn't really know what or who she's talking about.  
"I think it's time for me to head out." Not that he wants to leave, but it's late and he's sure Alexis is worried that he hasn't called. "Until tomorrow, Beckett."

She laughs, apparently finding his phrase amusing. "Goodnight, Castle."

He heads for the door, lingering a moment, wanting to stay. However, he reluctantly opens the door and waves goodbye to the lovely detective.

Once he's in the hallway, he inspects his finger again with fascination, part of it due to the healing and another because of the spark that seems to linger. He grins to himself, heading for the elevator, acknowledging that the night has solidified one thing for him.

Katherine Beckett is one extraordinary woman.

* * *

The next morning, Rick's greeted with a call from the lovely detective. Apparently, the victim is awake, alert, and willing to talk to them.  
He arrives at the hospital and sees Beckett waiting for him at the front entrance.

"Her name is Jane Hill and she's 25," the detective explains as they walk to the room. "Ryan and Espo found out she was awake earlier."

"And I'm guessing you wanted to do the honors?" Rick surmises. The quirk of her lips proves him right.

As they enter the room, he immediately notices the blonde young woman sitting up in the hospital bed.

"Hello," she greets. "You must be the detectives that have come to question me."

"I'm Detective Kate Beckett. this is Richard Castle. He's consulting with the NYPD for the case." A look of concern crosses Beckett's face. "How are this morning?"

"Better," Jane replies, her blue eyes brightening. "It's odd, I swear I remember him stabbing me, but apparently not."

"You just went through a traumatic event. It's common to misremember things," Beckett assures her. Guilt flashes in her eyes for a second before it disappears. Ah, she's not a fan of lying, then.

"That's what the doctor said too," the girl mumbles.

"You said your attacker was a man?" Rick questions, wanting to steer them away from the topic. Beckett shoots him a grateful smile.

"Yeah. We actually met online," the young woman explains. "We started talking a few months ago and then decided to meet in person. He wanted us to meet at the docks, since he'd known I was into that."

"And why would you be into that?" Beckett inquires, her tone free of judgement.

"The site we met on, it's sort of a speciality site I guess." Jane's cheeks redden and Rick raises an eyebrow. "Not kinky, mind you. It's more for people who believe they're mermaids or mermen. It's a forum of sorts."

"Mermaids?" Beckett blurts.

"Yep." Jane sighs. "The other girls who were murdered, Sissy, Charlotte, and Leila, they were my friends. We became so close and then they just…died."

Beckett grabs a tissue from the table and gives it Jane, who begins to dab her eyes. "If you don't mind me asking, why didn't you come forward about it? Also, the team didn't find any site like that when they want through the browser histories."

"I didn't realize it was them until about a month ago. I just thought they went offline, but then Sissy's mom contacted me via a private message, asking if I heard from Sissy. That's when I realized it was them. The reason why you can't find the site is because it's on the deep web."

"Okay," the detective soothes. "We are going to need the web site address though."

Jane nods, sniffles, and picks up the pad on the table next to her. She writes down the website and hands it to Beckett.

"Thank you." Beckett takes the paper from the young woman. "Would you mind sitting down with a sketch artist and describing your attacker?"

"Of course, anything to help," the girl responds. "I would give you his name, but I'm sure it's fake."

The duo smiles in understanding. "If you have any questions, or any more information, please don't hesitate to contact me." Beckett takes out her card.

"Okay," Jane says softly.

The two go to leave, but one question keeps nagging at the author.

"Jane, what makes you think you're a mermaid?"

The blonde lets out a bitter laugh, pulling down the right shoulder of her hospital gown, revealing a crecent shaped birth mark. "This. However, after last night, I'm starting to doubt it." She pouts.

"Right," Beckett says. "Anyway, please feel free to contact me if anything else comes up. We hope you get better."

She leaves the room, gesturing for Rick to follow suit. When they went out into the hallway, Rick asks,

"So, what do you think?"

"I think this address will be our breakthrough," she comments, waving the paper the her hand.

"You're probably right," he replies, rolling his eyes. "But I meant about her being a mermaid. Do you think she is one? And don't tell me they can't exist because your little demonstration last night proves that magic is real."

"I don't know, probably not," she replies, shaking her head.

"What makes you think so?"

She shrugs. "Were you attracted to her the moment you saw her?"

"No…."

"Then, she's not." She winks before heading to the front door.

"Wait," he starts, running after her. "How do you know? Beckett?" he whines, running after her.

Great, now she has him dying to figure it out.


	7. Chapter 7

AN: So, here's the next chapter. Thanks for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

After overcoming his brief moment of stupidity, Rick slides into the car, ready to interrogate the lovely woman beside him.

"So," he asks, his tone sly, "how would you know if that was a trait of a mermaid? The instant attraction, I mean."

She shrugs, appearing nonchalant, but the tension in her jaw denotes otherwise. "It was in that section of the book you showed me."

He smirks. "I only let you read about two passages of that book and nowhere did it say that instant infatuation. Also, I took the book back, so there's no way you looked further into the chapter."

She lets out a grunt of annoyance. "I must have heard it somewhere else then."

A small snigger escapes his lips, causing her knuckles to tighten around the wheel.

"So, let's say hypothetically," he starts.

"Castle," she warns, glaring.

"Hypothetically," he begins again. "If I were to think someone was a mermaid, would the ability to heal with water be an attribute?"

From his peripheral vision, she grits her teeth, closing her eyes when they arrive at a stoplight.

"Maybe…" she trails off

"And instant attraction to said mermaid would be another characteristic?" he goads.

"Perhaps," she answers vaguely.

A triumphant grin spreads across his face, the feeling of being closer to answers pumping adrenaline through his veins.

"So does that mean…" he suggests, giving her a knowing look.

Instead of replying, however, Beckett immediately pulls the car over, throwing it into park.

"Castle, stop," she pleads softly, gazing at him. "I'm begging you, if you value your life, you will not finish that question."

He studies her for a moment, realizing she's serious. There's a certain fear in her eyes, one he's never seen before now. Granted, they haven't known each other long, but Beckett is definitely not one to scare easy.

"Beckett, I'm not going to tell anyone," he assures, and he won't. He wouldn't betray her trust like that. He doesn't know if it's some mermaid magic or something as equally powerful, but he doesn't want to hurt her, at all.

"I know, I-," she begins, but shakes her head in dismay. "I can't do that. The consequences, for both you and me, but mainly you-" she sighs, pursing her lips. "It's not a good idea."

He pouts a little, but sobers up. Whatever is going on in her head regarding rules, laws, or regulations that she knows of must frighten her enough that she refuses to play along with him.

"But you showed me your-"

"I know what I did," she snaps. "I shouldn't have, but I couldn't help it. The trust I have in you is…undeniable. Dangerous almost."

He turns to face her, taking her hands in his. "Beckett, please, listen to me. I'm not going to harm you, your secret's safe with me." He gives her hands a gentle squeeze, trying to get through to her.

"I know, but it's not worth the risk. I'm not worth the risk," she murmurs, withdrawing her hands and starting the engine. "Come on, let's get back to the precinct. I'm Ryan and Espo are wondering what's taking us so long."

As she drives, he sits back, contemplating what she's said. So, she doesn't think she's worth the risk, huh? Even for this…whatever it is between them. There's something there, he just doesn't know what to call it. However, he's pretty damn sure she is worth it.

He'll just have to prove it her.

* * *

About a half hour later, the duo sits in front of the projection screen at the precinct, preparing to peruse through the website Jane had given them. Accessing it had been easy, since it wasn't a hidden site on the deep web. Jane was even nice enough to provide them with her username and password. While Rick probably wouldn't be as open in terms of sharing information, it does make their investigation easier.

"Seems like a pretty innocent website," he remarks. He's traversed through the deep web for research, discovering some pretty weird things and some fairly terrifying things. The site in front of him fits neither category, the webpage adorned with a sea background and a calming ocean breeze as the soundtrack. "What's it doing on the deep web?"

Beckett shrugs. "Probably a way to make the group feel special, like they're a secret society or something."

He nods in understanding. It probably gives them further sense of camaraderie, besides their supposed suspicions.

"Let's look at Jane's private messages," Beckett's remarks, going to the young woman's profile. The description box is empty, save for Jane's age, hair color, and eye color. Her inbox is barely full. After scrolling through various site announcements, the duo finds what they're looking for.

"Okay, it looks like she received a message from merbuff234 last week."

"Merbuff?" Rick snorts.

"He invited her to come and meet him. After she said okay, he gave a her a description and where to meet him. So, it sounds like he does live in New York. Also, looks like they've been corresponding for almost five months, according to these messages."

He frowns, eyes skimming over the text. It's not much to go on and when clicking on the profile, the guy's page is completely empty. Perhaps it's one of multiple accounts?

"Any messages from her friends?"

Beckett sighs. "Doesn't look like it. They've must've communicated by text."

"If so, why couldn't Jane tell when her friends went silent?"

"Maybe they had a habit of disappearing and reappearing when they wanted to talk?" Beckett purses her lips. "I wonder what threads Jane frequents."

The detective clicks through various conversations Jane's participated in throughout her time on the site. Most consist are discussions of symptoms in regard to many users' "condition". As they read, Rick notices a quirk of his partner's lips and the occasional roll of her eyes as they wade through the conjectures of various unknown people. He wants to ask what they real traits are but he prefers not to see that devastated expression on her face again.

One conversation piques their interest. It's about various places that mer-people could reside, including cities and locations in the ocean. It appears that Jane had some friendly banter with merbuff throughout the thread, bonding over the fact that they both live in New York and how they frequent the aquatic spots in the city. It appears as though this is how their relationship began.

"Says his name is James, but of course we don't know if it's true or not." Beckett huffs before groaning. "Hopefully, her description to the sketch artist will help us. We should also ask her if her friends ever mentioned being contacted by merbuff or someone similar."

"Also, maybe we should check out some of the spots mentioned on the postings. Maybe he actually did visit those places?" Rick suggests.

"Hmm, maybe. Once I get the sketch back, we can start looking. We can question her tomorrow. Poor kid has had a long day and night."

Rick smiles, admiring the small display of sympathy from his partner.

"So, what do you want to do now?" he inquires.

"Look over the other victims' files again. See if we can connect anything with our new information."

They grab the files and sit at Beckett's desk. About halfway through, Castle notices her mug is empty and gets up to refill it for her, winking as she tosses him grateful smile. As he works his magic with the coffee maker, he makes a mental note to replace the ancient machine with something with better tasting coffee. Maybe a nice espresso machine? It has to be something he can create Beckett's coffee in, which he had figured out the recipe for a few days ago. Apparently, she likes vanilla. He thoughts wander, wondering how much she's actually into vanilla-

His mind is so distracted that he doesn't notice the hazard that is the chair near Beckett's desk sticking out. The bullpen is empty, save for one or two other officers on the other side of the room, so he has no clue who could have moved it. Nonetheless, his shoe gets caught, making him go flying into his own chair and the cup freeing itself from his grip. The author's eyes can only watch in horror as the coffee spills onto Beckett's arm, guaranteeing third degree burns. However, there's no scream, no gasp. Instead, his partner looks at her arm in shock before scowling. Slowly, the beverage is absorbed into her skin, leaving no trace of an injury. A minute later, there's no evidence of the liquid, with the exception of some stains on the paperwork.

He gazes at her, eyes wide. She just shrugs.

"I told you the needle wouldn't work on me," she replies simply before returning to the page in front of her. "I'll change my top later." He chuckles, shaking his head as he goes to the break room to retrieve some towels.

He's looking forward to seeing what other powers she has in her arsenal.


	8. Chapter 8

AN: So, here's the next chapter! Thank you for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 8

The sketch artist does come back with an image, but it's hours later and too late for Rick and Beckett to do anything. Thankfully, though, the image is fairly detailed, so they can get an early start in the morning.

"Unfortunately, there's nothing unique about him. No piercings, tattoos, or scars," Beckett grumps as they leave the precinct.

Rick shrugs. "At least we have a sketch," he offers, but she's right. The description is fairly generic. Clean shaven, square jaw line, somewhat quaffed brown hair, and blue eyes. However, hopefully the picture will help them as they scour the sights the next day. "So, you up for some food or…?"

She snickers. "Jeez, Castle the amount of times you offer me food, you'd think I was starving myself."

"Just looking out for your well-being, Detective," he chirps.

She shakes her head, but he spots a smile on her face. "Thanks but no thanks, I've got stuff at home."

He sighs dramatically. "If you insist."

"Night, Castle," she says heading toward the direction of her apartment.

"Until tomorrow, Beckett," he answers.

He watches as she walks away, happy to see that the tension from earlier is nowhere in sight.

Instead of hailing a cab to go home, he takes a detour to a small florist near the precinct. The evening hour means there's a lull in customers when he arrives, which is what he needs.

"Good evening," he greets the bored looking teen, who is on her phone. He peers at the name tag. "Trisha. I was wondering if you could help me with making a selection?"

The girl brightens, seeming genuinely interested. "Sure, what can I do you for?"

"I was hoping you would know of any flowers that are usually found on the ocean floor?"

Trisha squints, furrowing her eyebrows in thought. "We don't have much of a selection, despite it being mid summer." She trots over to a case, which is filled to the brim with various arrangements. "The most common one is water lilies and it appears it's the only one we have left in stock," she states, giving him an apologetic shrug.

"That's fine. I'll take one of the small displays."

After paying, he leaves, wholly satisfied. The arrangement is nice, a small glass case containing one white and one pink water lily, with bright rocks at the bottom of the vase. Beautiful, but unassuming, just like someone he knows.

When he arrives back at the docks, he places the bouquet on the lower part of the boat, where one could easily reach up and grab the flowers. He attaches a note, snickering to himself as he writes.

He calls Alexis for his daily check in as he prepares a quick dinner. He wishes he were sitting across from Beckett, but it looks like that will have to wait. As he talks, his daughter notes something that he himself doesn't realize.

"You sound a lot happier, Dad," she says after he finishes talking about his day, obviously leaving out the more magical parts. "Definitely not as bored as you were before."

"Well, it has become more interesting," he replies. "The stuff the NYPD does is just fascinating, except for the paperwork."

She chuckles. "Are you sure it's not because a certain detective is interesting and beautiful?"

Hmm, had he said that? Well, it is true anyway. "It might be part of it. In all honesty though, the police work is intriguing."

"Enough for a book?" she prods.

He rolls his eyes. "Maybe." The plot is still rattling around his head, but it needs some refining before he begins to outline it.

"I hope so," she teases. "Anyway, I have to go, Paige is calling."

"Night, Pumpkin," he says before hanging up.

He polishes off his dinner and prepares for bed, finding himself going to sleep more often, the insomnia nowhere to be found, probably because he has to wake up so early lately. The one thing he won't miss once he's done renting the boat is the small space. He longs for his large bed. Besides, no way would he try to romance Beckett in the cramped space. Well, at least he hopes he'll be able to charm her. That remains to be seen.

So, he drifts off to sleep, his dreams filled with him and a certain hazel-eyed detective at the beach and in the pool at his Hamptons house. However, she has a long, elegant tail. What color though, he can't tell, because it keeps changing from scene to scene. Regardless, she's just as beautiful as she is with legs, maybe even more.

When he wakes in the morning, he checks the spot where he left the flowers. To his delight, the piece is gone.

And in its place is a seashell.

* * *

When the duo rolls up to the boardwalk entrance of Coney Island, they're lucky enough to find a parking space during the summer rush.

"Ahh, Coney Island, home of fast food, amusement, and occasional depravity," Castle states. "I loved coming here as a kid."

"Why doesn't it surprise me?" Beckett teases as they stroll the boardwalk toward the aquarium.

"What? You don't like Coney Island? It's a New York staple!" He can't imagine any New Yorker who doesn't enjoy themselves among the various activities during the season. "Please tell me you've at least ridden The Cyclone."

"Of course I have." She sighs. "I've been here enough times as a kid, but being with the NYPD kind of destroyed the joy of it for me. Now all I see is the potential crime that can happen."

He pouts, but understands. "Well, maybe I can restore that enjoyment for you."

"We're here to find a murder suspect, not spend a day on the rides," she mutters. However, she glances toward the famous hot dog stand. He makes a note to buy two of those later.

"So, is it safe to assume that you've never been in the Mermaid Parade?" he jokes, giving her a gentle elbow nudge. He's almost afraid he'll receive the same glare as before, but instead she snickers.

"Never have, never will. I gave up waving the girls around once I was done with Vice."

He swallows, the visual of her in a mini skirt and tight top with sexy heels almost stopping him cold.

"Even in private?" he chokes out, still able to keep up.

She raises an eyebrow, eyes roaming his body. "That remains to be seen." She gives a wink before heading into the aquarium entrance.

A low groan escapes him as he follows.

That woman is going to be the death of him.

* * *

"Yeah, I've seen him," the manager of the aquarium, Carlos, states as he gazes at the sketch Beckett shows him.

After going through a few of the employees who couldn't place their suspect, the manager seems to be much more helpful.

"I mainly remember him because he kept taking pictures of the displays. I had to tell him to turn the flash off because it would disorient the fish. Guy was polite enough, but he gave off a weird vibe." The manager lifts his shoulders in defeat.

"Was anyone with him?" Rick asks.

"Nah, just him," Carlos replies. "Though he was one his phone a lot. Which I know is nothing new these days, but he seemed to be texting the pictures to someone."

The duo exchanges a look, both with raised eyebrows.

"How long ago was this?" Beckett quizzes.

"A few weeks ago, just right after the Mermaid Parade actually. He didn't say much, just took pictures and left when he was done."

"Okay, thank you," Beckett says, handing him her card. The partners depart the facility, returning to the boardwalk.

"So, who was he sending the pictures to?" Rick asks. "Jane?"

"Maybe," she guesses. "In order to give more validity to his story, it would make sense. However, no such pictures were on her phone or the messages we read."

"So, what's he doing with them?" he asks.

The sound of Beckett's phone ringing interrupts them. She answers, listening to whoever is on the other end. After a few minutes, she hangs up, pursing her lips.

"That was Ryan," she says, glancing at Rick. "It appears our guy was also at the Bronx Zoo about two months ago and took pictures of the aquatic habitats. Ryan and Esposito are looking to go to the next spot, which is Central Park Zoo."

"And I'm guessing no one was with him?" he surmises.

"Exactly."

They stride along the walkway, taking in the crowd and buzz of activity. He's tempted to ask her to walk along the beach, but realizes it might be hazardous to her feet.

"Come on, let's make a quick pit stop for lunch. We can eat it on the way to the car," he offers. She accepts, rolling her eyes and mumbling something about men and their stomachs.

They enter Nathan's Hot Dogs Restaurant and he immediately goes to the 'To Go' counter.

"What do you want?" he asks.

"I can go for a Super Cheeseburger, a soda, and fries." He grins, no longer surprised by her voracious appetite. "I'll make up for it with a good workout later." He's craving seafood himself, but briefly wonders if that would be disrespectful. She must notice him glancing over that part of the menu, because she says, "It's fine, Castle. I do eat fish."

His expression turns confused, but he doesn't ask. He orders and a few minutes later, their food comes and they're heading toward the car.

"So, you eat fish?" he inquires. "Isn't that like going against your kind or something?" Nevertheless, he takes a bite of his shrimp.

"How else would my kind survive? The ones that live in the ocean, I mean. Eat seaweed and plants all the time?" She lets out a derisive snort.

"Well, yes," he says. "And maybe human flesh?" He winces as soon as the words come out of his mouth.

She laughs, loudly to the point passersby give a quick look. "No, no one feasts on humans. I can promise you that."

"Guess Barrie got that one wrong then," he grumbles.

"He never said that humans were devoured, just drowned." Regardless, she shakes her head in amusement. "And no, we don't do that either. At least not the ones I've met."

"So, your alluring looks don't make sailors crash into rocks?" he teases.

They arrive at the car, Beckett of course going for the driver's side.

"Most of those are tales were fabricated to give them something interesting to talk about when they got home," she clarifies. Chuckling she says, "Besides, it's not our fault that men are so easily distracted."

His expression morphs into a scowl as she starts the car. "Well, I mean, I can see why."

She shoots him a playful glare. "Alright, enough of the mythical creature talk."

Unable to restrain himself, he replies, "Wait, one more question!"

"What?" she whines more than snaps.

"How old are you?" He has the decency to look sheepish.

"Don't you know it's rude to ask a woman's age?" She chuckles. "I'm thirty three."

"So, no weird age difference or immortality.'

"Not unless you consider a what? Eight, ten, year difference strange."

"It's nine and no, I don't."

"Good. Now, let's focus on the case. Hopefully Ryan and Espo will have more once we get to the next location."

"Which is what?"

"For us, it's a diving instructor."

"Diving instructor? Wow, this guy went the extra mile, if he signed up for lessons."

"Yeah, well, people can get pretty desperate when searching for never ending life," she mutters. "I sometimes wonder if-" She stops herself, but he has a feeling he knows what she wants to say.

"Your mother was killed because someone wanted to live for eternity?" he continues gently, not wanting to upset her. Both of her parents were merpeople, so it would make sense if that was the real motive behind her mother's murder.

"Yes, but it doesn't fit. The circumstances needed to obtain it weren't even closely followed. So, I don't think that's it."

"Unless, the person was inexperienced and just thought killing her was enough."

"Maybe." She bites her lip, closing her eyes. "I don't know. She was so cautious. Both her and dad were so careful with hiding what they were and what they could do. I highly doubt that anyone would've known. I mean, I've heard stories of people who have discovered the eternal life of mermaids and their attempts to obtain it. However, they're usually pretty close to the mark in regard to how they're supposed to get it."

They're halfway to the location and Rick can see this conversation is taking its toll on her.

"One day, we'll find the person responsible," he assures her. "Now like you said, let's focus on the case."

She tosses him a grateful smile, resolve in her eyes, her passion for finding justice further ignited.

"So, do you think we should go for a diving lesson?"

"Castle!" she scolds, but her lips twitch. Good, he's cheered her up, made her happier.

He holds onto the hope that he can always do that.

* * *

AN: The Barrie comment is a reference to J.M. Barrie's depiction of mermaids in his play and novel, _Peter Pan_.


	9. Chapter 9

AN: So, here's the next chapter. Thanks for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 9

The duo arrives at the diving place twenty minutes later. The building appears to be a quasi-remodeled warehouse, with a sign reading "Lucy's Luxury Diving" across the top. As it is summer time, the warehouse is full of patrons, ranging from young to old, most preparing or in the middle of instruction. It takes a moment to track down the supervisor, Lucy, and when they do, she has no trouble telling them what she knows.

"Yeah, him and another guy came in here right before the summer season started," she says as she prepares what looks like to be a diving kit.

"Someone else was with him?" Rick inquires.

"Yeah, had the whole celebrity get up too. Baseball hat, sunglasses, even had a fake beard. I didn't recognize him myself, which obviously was the point."

"How do you know it was fake?" Beckett asks.

"I've been in the business long enough to know when celebrities are on the prowl." Lucy chuckles. "It doesn't fool me anymore, but I let them have their privacy. They're just here for lessons, not to be hounded." She shakes her head, seeming to recall something. "Last celebrity that came in here almost got mobbed by a bunch of fans. Then again, she wasn't exactly trying to hide who she was."

Rick laughs, knowing what that feels like. He's usually okay with it, unless he's trying to have a day out with Alexis.

"What's so funny?" the supervisor asks, shooting him a puzzled look.

"Er, nothing. Just empathizing with a fellow star." He grins, but the confused expression remains. He pouts, causing a snicker from Beckett. He thinks the woman would have seen his book jackets, at least.

"Anyway, did either of them ask any questions?" the detective prods.

"Some. The guy in the sketch just wanted to know the mechanics and how-tos of diving. He seemed more interested in the actual lesson than the other one."

"What did the other one want?" the author questions.

"He asked more about like the best and deepest diving spots around the city. Asked a lot of questions of about marine life and mythology." Lucy shakes her head. "I swear the dude was looking for something, but I wasn't sure what. I was able to answer some of the questions, but he definitely left unsatisfied. Oh well, you can't please everyone." The woman shrugs, packing up the set.

"Right," Beckett murmurs. "Was he specific about what type of mythology?"

"Yeah, actually, mermaids. Guess he's one of those crackpots who believes in that stuff. Why?"

"We think the murders might be linked to them," Rick offers.

"Huh." Lucy cocks her head. "Wish I could help you more, but that's it. Also, I have a lesson to teach."

The duo lets her go, requesting that she call if she remembers anything else.

"What do you think the guy was looking for?" Rick asks his partner. He receives a lift of her shoulders in response.

"Beats me." She's quiet for a moment, her eyebrows scrunching in thought. "Maybe he's trying to figure out if there's any possible living spaces?" She sighs, scratching the back of her neck.

"He's looking for Atlantis or something?" Rick questions. "Wouldn't be that in the middle of the ocean?"

"Not necessarily that one," she responds. "There are colonies spread across the world. Atlantis is the big city, the main one. All of the other villages are ruled by Atlantis. I wouldn't know where they are though, with the exception of the two that are in New York."

"There's mermaid towns here?" he exclaims, voice full of wonder.

"Yeah, I mean we do have the Hudson River and the Atlantic Ocean. I've only been to them a few times."

"Huh." It astounds him that there is actual mythical life swimming around New York. Then again, something tells him he'll never get over it.

"If they're looking for the colonies, they must know there's a chance of screwing up with just picking girls from the website," she grumbles. "Which means the killers have done their homework and this case just became a lot more dangerous."

The author nods, realizing what it could mean if someone found a whole hamlet of merpeople. They reach the car, entering simultaneously.

"So, let's head back to the precinct and hope Ryan and Esposito found something too."

"Right."

The duo drives off, both wishing to close this case soon.

* * *

Unfortunately, Ryan and Esposito have little good news to share. The zoo keeper had told them the same thing that all four had been informed of regarding the suspect and his behaviors around water exhibits. The two male detectives had also stopped by Jane in the hospital to see if she knew anything about another merbuff floating around the website and interacting with her friends. She had said she remembered Charlotte mentioning someone in passing, but nothing ever came of it. She had given Ryan and Esposito the others screen names so the detectives could look at the girls' posts.

"At least we have these," Beckett comments at the piece of paper Ryan hands her. "And the fact that the guy in our sketch has a partner."

"It does kind of make sense," Rick comments. "It would be hard to lure these girls in enough time to kill them. They're probably splitting up the job, one lures them, the other kills. Or they alternate."

"The diving instructor said the other guy had a celebrity get up," Beckett responds. "If he is someone well known, I doubt he'd get his hands dirty."

"True," Esposito comments. "But at least we have some type of breakthrough."

"And part of it is thanks to Castle's haired brained idea to drag Beckett out on a boat," Ryan teases, playfully nudging Rick with a manilla folder. The author beams in pride, while Beckett just rolls her eyes.

"Don't stroke his ego, Ryan, it's big enough," she mutters, her lips twitching upward.

"That's not the only that's big," Rick mumbles, smirking. He swears her eyes flick to the aforementioned body part, but it's too quick and her face twists in faux disgust.

"Okay, back to work. Let's go through each of the girls' postings," Beckett announces.

The team splits up the postings; Castle and Beckett taking Charlotte and Leila, and the boys focusing on Leila. Castle and Beckett sit at her computer, clicking through the various conversations the girls had been involved in. Unfortunately, they're not finding much, which is fine because Montgomery ushers the duo into his office a few minutes later.

"I just got a call from the mayor, wanting an update in regard to the case," he says.

"Oh?" Rick inquires, raising an eyebrow. He had hoped the mayor would refrain from checking in for a little while longer. The expression on Beckett's face informs him that she shares the sentiment.

"Yes, he seems very delighted at the progress made. Which, of course, began when his good friend Rick began helping. His words, not mine." The captain purses his lips, fighting the grin threatening to form. Before Beckett can object, Rick chimes in.

"I'm just a small piece of the puzzle," he states. "You guys would've gotten here. I just…expedited it, that's all." He sneaks a glance at his partner, who appears somewhat appeased, though she's scowling.

"Right," Montgomery says. "Anyway, keep up the good work. And please, try to close this case before the next full moon, yes?"

"We'll try our best, Captain," Beckett responds. The captain dismisses them and they return to her desk. Rick can sense she's none too pleased about the conversation regardless of the mayor's praise, as she's definitely not someone who has any desire to appear incompetent. The scowl stays in place as she silently continues perusing Sissy's posts.

"Hey, why don't I cook you dinner?" he offers, cracking a smile. The hazel irises glance at him briefly before returning to the screen. "Your place, not mine. I promised Mother the whole loft to herself for the summer, unless of course she decided to go to the Hamptons." Silence. "I swear I'm a really good chef."

She snaps her head up from the computer, eyes narrowing into slits. "Food doesn't solve everything."

"Then flowers? A seashell?" he jokes. He spots a hint of her lips turning upward, but of course, it vanishes. Damn, she seems to really have taken the mayor's comment to heart. "Look, Beckett, if it helps, I don't agree with the mayor. All of the progress has been made by you guys. I'm just a consultant."

"Yeah, but Ryan is right. All this progress is because you suggested to take that boat ride."

He shrugs. "You would've done it eventually, consequences be damned." He's sure she would, even if she shackled herself to the boat in order not to fall into the water.

"Mmm," she replies. Then looking up from the keyboard, she says, "I am craving Italian. Think you can handle that?"

He beams, not even hiding his giddiness. "Sure. I just need enough time to gather the supplies."

"Okay, then let's meet at my place at eight."

He agrees and she lets him in on what she's found, which isn't much. Apparently, both girls had interacted with different men on the site. As she read the conversations, the two men sound completely different, each tailored to the girl's personality.

"There's a few references about pictures here, so it sounds like they were sent something," Beckett mutters.

"It can't be through the site," Castle states. "From my own research, if a person is no expert on the deep web, anything uploaded on it can be tracked."

"Great," the brunette huffs. "Guess it's something we'll have to leave until tomorrow then." She's reluctant to quit, which is no surprise, but they've hit another dead end and evening has come upon them. "I think our next step should be to look to see if any other girl is being chosen on the site. Hopefully, that will provide us with a trail." She picks up her bag and Castle stands up. They wish the boys a good night and enter the elevator.

"So, any type of Italian in particular?" he asks. His stomach is longing for spaghetti and meatballs, but he'd rather give her the choice.

"Surprise me," she replies, grinning, eyes light with teasing.

He's more than happy to accept the challenge.

* * *

He arrives at her apartment just a little before eight. It had taken him long enough to gather the ingredients required for the dish he plans to make. With one hand cradling the grocery bag, he raps on his knuckles of his free hand against the door. She answers a moment later, and he swallows, feeling his blood pump faster at the sight of her.

She's donning a white robe, tied tightly with a narrow string, but he can still see a smidgen of a white blouse underneath. However, it's the realization she's not wearing any slacks, thus showcasing her long, toned legs, that leaves him almost speechless.

"Did you call this off?" his asks, unsure. His phone never rang, as far as he can recall.

She shakes her head, opens the door wider, and gestures for him to enter. "Close your mouth, you'll catch flies that way." She smirks.

He crosses the threshold and his ears perk up at the sound of…running water? From the bathroom?

"You leave the sink on?"

She rolls her eyes, laughing. "Nope."

He glances at her again, eyes examining her outfit once more. She's wearing a robe, no pants, but still has on a shirt. There's running water, but not from the sink. Maybe the bathtub? Wait, if it is from the bathtub, then that means…

"This isn't going to be a normal dinner, is it?" His heart beats fast at the implication, excitement running thorough his veins again.

"It's us, Castle. I don't think anything will ever be normal with us." There's no lamenting in her tone, only good-natured ribbing. "But yes, you're right. Now come on." She strides toward the bathroom, not even waiting. He sets the groceries down on the counter before scurrying after her, restraining himself from cheering aloud.

He's about to see Katherine Beckett in all her mermaid glory!


	10. Chapter 10

AN: So, here's the next chapter. Thank you for the follows, favorites, and reviews for this story. I really appreciate them! Also, Happy Mother's Day to those celebrating it!

Disclaimer: I don't own Castle.

* * *

Rick enters the bathroom just in time to spot Beckett disrobing in front of the good-sized claw foot tub she possesses. When he'd visited the first time and used the facilities, he'd been astonished at the size of it, curious as to why she'd have a tub so big. Now he knows.

"I thought about doing this at the beach, but with the summertime..." she says, shrugging at the unspoken danger.

"Right," he replies, licking his lips at the sight in front of him. Kate Beckett in nothing but a blouse and black boy shorts. In her bathroom no less.

"Focus, Castle," she gently scolds, unbuttoning her shirt and throwing it to the floor, leaving her only in a white bra. She raises an eyebrow, smirking as she stands, hands on her hips. She's a vision, with nicely toned abs and legs, narrow hips, perfect breasts, from what he can see, and one sexy smile.

"You're making it extremely hard to," he mutters. His focus isn't the only thing becoming strained. If Beckett notices, and he's certain she does, she doesn't comment. Instead, she steps closer to the bath.

"Ready?"

"Yes!" His tone shifts to that of a little kid on Christmas.

Rolling her eyes, she lifts one tentative leg, dipping her foot into the tub. With more confidence, she adds the other foot and a minute later, she immerses herself in the water. He approaches the tub and sees the water shimmer, almost glow, around her legs. The shine moves along until it reaches her neck and stops, slowly fading. As it does, he realizes her body has grown longer, her upper body pushing farther upward.

His gaze moves toward her feet again, and sure enough, she's sporting a fin.

"Hold on," she says, gesturing for him to move aside. Then, with impressive arm strength, she pushes her body out of the bath and plops herself down on the toilet lid. From this vantage point, he's able to examine her new form more closely, and no surprise, she's enchanting.

A gossamer fin tip flicks around as he observes her, the ends brushing the floor tile. The translucent tips feed into one long, gorgeous, almost glittering, purple tail that finishes around her hip, pieces of the same material as the ends surrounding her waist. Her torso is pretty bare, with the exception of a shell-shaped black brassiere.

"So?" she quizzes with a smile, tail swishing playfully.

"You're beautiful," he breathes, eyes roaming her shape. Unable to contain himself, he asks, "Can I touch it?"

She chuckles. "Sure."

Placing one hand on the tail, he gently rubs it. To his surprise, it doesn't feel too scaly, more smooth, almost like...satin?

"It's part of the allure," she explains, sensing his confusion. "They're scales, but to humans it feels nice and soft." She wiggles the appendage.

He gently strokes, moving his hand up and down, enjoying the sensation of her lightly shaking her tail. It appears she's relishing in the massage as well as her head leans back, eyes closing, a carefree smile on her face.

"I've never had someone touch my tail before," she admits with a hum. "It's nice."

Her tail twitches again, seemingly in happiness. Hmm, interesting. He makes a mental note to revisit that later.

"Okay, that's enough." She sits up. "Can you please toss me the towel so I can dry off? You can cook us dinner while you're waiting." She gives him a full on grin, and he chuckles as he hands her a cloth. Something tells him he'd never say no to anything she asks.

"Okay, okay, but I still have questions."

"Of course." She nods, shooing him away.

He shuts the door on the way out to give her some privacy.

Now, time to cook some dinner.

* * *

Kate stares at the towel in her hand, her mind still processing what just occurred. She begins to dry herself off, her brain going into overdrive. Castle just saw her in her mermaid form.

And is fine with it.

Okay, well, the him being fine with it doesn't really shock her. It's more of the fact that he was so gentle about it and respectful. She's heard tales over the years of what has happened when a human sees a mermaid in their true from for the first time. The person is usually shocked and then is overcome with lust and attempts to pursue the mermaid. It apparently has to do with the type of pheromones merpeople give off or something. However, Castle did none of that. What it means, Kate has no idea. All she knows is that she likes him touching her tail and wouldn't mind if he does it again.

As she finishes drying, her tail disappears, legs replacing it. She kicks her feet, happy to have them back. While she doesn't hate her mermaid form, she's more comfortable with her human parts.

Walking into her bedroom, she combs through her dresser until she finds something cozy to wear. As she throws on a pair of yoga pants, her nose catches a whiff of something from the kitchen, hints of oregano, garlic, and other ingredients swirling in the air. Mmm, smells delicious.

She pads into the kitchen, stopping and taking in the sight in front of her. Castle is moving around the space as if he belongs there, stirring something in a pot before opening the oven.

"Hey," he greets. "I settled on chicken parmesan, if that's okay with you."

"It most certainly is," she replies, taking a seat at the counter. Raising her eyebrows, she smirks. "So, come on, I'm sure you're exploding with questions."

He pouts playfully, digging out some plates from her cabinet. "Does it hurt?"

She shakes her head. "Nope, never has. It's pretty uneventful, with the exception of the glow." One of the thing she's thankful for, particularly since she shifts so often.

"You said no one's touched your tail before, so does that mean no one else has seen it?"

She sighs. "Yeah, only my parents and you know what I am. No one else has ever seen it." She always ensured that any guy she'd been with, the few that there were, left before she cleaned herself up.

The mischievous smile on his lips hints at his next question. "What happens with your clothing?"

She snickers. "It comes back," she responds as he serves her a plate. She inhales, almost moaning at the smell. "Why, I don't know. But it does make it more convenient to change back." Running around New York City naked is not her ideal way to spend time. She may be soaking wet when turning human again, but at least she's clothed.

She notes a flash of disappointment in his eyes, but it vanishes. She rolls her own, before asking, "So any other questions, or can I eat?"

"I'm done...for now," he teases.

She snorts, taking a forkful of the dish and bites. Mmm, it tastes as divine as it smells. Oh, which reminds her, she should probably mention that other little factoid.

"Also, my senses are a little heightened," she says. "Not a lot, but for example, I can smell some of the different ingredients in the sauce and I can hear your heartbeat, but it's muted."

It surprises her, how easily the information spills from her lips. It doesn't bother her to share all of this with him, but it should. She internally groans at the thought. The elders are going to have a field day with this the next time she sees them.

"That's so cool!" His eyebrows furrow. "But wait, if your senses are are higher than a human's, how come you didn't react to the hot coffee?"

"If my body senses something dangerous, it dulls my feelings and attempts to protect me from it. Its usual reaction is to just absorb it."

"Huh." A contemplative look crosses his face and then he shrugs. I

They eat in silence for a few minutes, both polishing off their plates quickly.

"Wanna watch a movie?" he asks. He doesn't seem to want to leave, and if she's being honest with herself, she doesn't want him to.

"Sure."

She rifles through her sparse DVD collection and finally picks a movie.

"John Woo?" he questions, his tone conveying surprise and joy.

"Yep! Glad to see you're a fan too."

Given her lack of a television, they settle for viewing it on her laptop. It requires close quarters, with them almost snuggled up to each other, but neither complains.

The day catches up with her eventually, her eyes slowly fluttering closed in the middle of an intense action scene. Her head leans into Castle's shoulder and soon, she's fast asleep.

She thinks she hears him chuckle.

* * *

About an hour later, the credits roll on the screen. Castle sighs, closing the laptop, his free hand gently stroking the ends of Beckett's hair, reveling in the softness of it. She must sense his touch because her eyes open halfway, her expression groggy. It's adorable.

"Hey," he murmurs. "I think it's time for me to head out."

"Okay," she grumbles, getting up. He swears she pouts, but it disappears.

"Thanks for having me over," he says as she follows him to the door.

"Well, you are persistent," she jokes.

"Mmm hmm," he hums. He won't even deny it at this point. "Well, until tomorrow." He glances at her for a moment before slowly leaning in, his lips ready to press a chaste kiss against her cheek. However, she must have other ideas since her head turns, causing his lips to touch gently against hers, their mouths moving in sync.

It only lasts for a moment, but the feelings the kiss evokes in him are indescribable. Dare he say it, magical. He craves more, but doesn't want to overstep.

"Goodnight, Detective." He steps away, his body flooding with warmth.

"Night, Castle," she replies, a smile on her face, eyes dancing with mirth.

He opens the door and steps out, his fingers touching his lips as he walks down the hallway. He can't believe he did that, not that he regrets it. Also however brief, his lips had caught a taste of something sweet, but he can't put a finger on what it is. Regardless, he desires more.

Hopefully, Beckett does too.


	11. Chapter 11

AN: So, here's the next one! Thank you for all the follows, favorites, and reviews for this story. I really do appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 11

Rick arrives at the precinct the next morning, coffee and bear claw in hand. When he steps onto the Homicide floor, he's greeted with a few nods by some of the officers as he approaches Beckett's desk.

"Good morning, Detective," he announces, setting the items down on the wooden surface.

"Morning, Castle," she replies, tossing him a small smile, eyes shining, before returning her gaze to the computer monitor. "Ryan, Esposito and I are going through the site, again."

"Any luck yet?" he inquires. He knows it's going to take a while for them to find an interaction similar to what their killer does, but hopefully they find it before the next full moon.

"Nope." She grimaces. "No one's been approached, male or female. Maybe the guy's waiting?"

"Can't wait long, though," Rick points out. "It's only three weeks until the next full moon."

She hums in agreement, pursing her lips in thought. "I wonder," she murmurs to herself. Then, she turns to him, eyes brimming with curiosity. "Based on your supposed knowledge of the deep web," she teases, "do you know how difficult it would be to register for a site like this?"

He raises an eyebrow, thinking. "Well, it's not well hidden, and there's no special invitation needed, so my guess would be not it's that hard. Why?" However, he's pretty sure he has an inkling of what's on her mind.

"I think we need to draw this guy out," she states. "And the one way to do that would be to create a profile on here."

"So, you want to join the land of crazy conspiracy theorists, huh?" he jokes.

She rolls her eyes. "Har har. I'll take a look at the registration stuff and see if I can get myself in."

"Do you want Ryan, Esposito, and I to make one?"

"Probably not a good idea," she answers. "It might look weird if several people create account all at once." She lifts her shoulders in a shrug. "Besides, I have the advantage of being a little more, authentic, shall we say." She smirks.

"Ah, I get it." He chuckles. "Alrighty then."

As she digs into the registration process, he looks up areas she can discuss when she's up and running. He's curious to how this will work, since she is a private person. Something tells him she might need some assistance when it comes to interacting on social media. On the other hand, she may surprise him.

It wouldn't be the first time.

* * *

About a half hour later, Beckett lets out her fourth grunt of annoyance.

"How's it going?" he questions, looking up from his phone. From the sound coming from her lips and the adorable scowl on her face, he assumes 'not good'.

She huffs. "I never thought I would hate a questionnaire so much. I'm on page three and I still have four pages to go!" He swears her glare could burn a hole through the computer screen.

"The admins probably want to make sure the people are serious about signing up and not just there for laughs." The people on the site seem pretty serious about their beliefs, so it wouldn't surprise him if they didn't welcome those outside their circle who weren't sure of their 'condition'.

"Yeah, probably," she mutters, typing away.

"You can't get the tech person to just hack in?"

"Eh, I'd rather not. I don't want to raise any type of alarm."

Rick nods, returning to his phone. Thankfully, he's found plenty about nautical life that he can supply Beckett with the information when needed. So, he decides to distract himself with the latest app. He would examine Beckett and admire those lovely cheekbones, the slender curve of her neck, those pouty lips, think about what it would be like to kiss her again, but alas, she finds the staring creepy and she is definitely not in the mood for him to be annoying her. So, he settles for staring at a bunch of candy on a screen instead.

He's not sure how much time passes, but eventually a sigh of relief escapes his partner's lips.

"Finally," she groans, her chair rolling backwards as she pushes against the desk. "I'm done!" Her head leans on the back of the chair. "Now I have to get approved. I have no idea how long that'll take."

"Maybe they'll let you know by tomorrow," he remarks brightly.

"I'm hoping," she mumbles. Her finger is posed over the mouse and she clicks, eyes blinking in surprise. "Huh, that was fast." She quickly scans the screen, eyes rolling in half amusement, half annoyance.

"Guess you were right," she says, smiling. "The questionnaire was a test, it seems." Reading aloud, she states, "'Congratulations for completing the extensive questions. Since you were able to finish the survey, you are now able to access the site. Have fun with your new mermaid friends!' Well, time to get started."

"Did you set up a user name?" he inquires.

"Yes." She bites her lip nervously.

"And?" he pushes, receiving only silence.

Oh, now he needs to know.

He peers around the monitor, almost pushing the brunette out of the way to see what her brain thought up. She lets out a small whine at his snicker.

"Purplemermaid79?" he teases.

"It's the first thing that popped into my head." She gives him a shove. "Anyway, time to get started." Tilting her head in thought, she furrows her eyebrows. "What should I say?"

"Put yourself out there," he replies.

"Put yourself where?" Ryan asks, approaching the desk. "What've you guys been up to?"

"Beckett is now a proud member of the mermaid forum."

"It's for the case," Beckett explains with a snort.

"Ahh, digging deeper, I see," the Irish detective remarks. "Want us to do anything?"

"See if you and Espo can pull the posts we printed out a few days ago. I want to see what it was that drew our killer to these girls, get a better feel for what I should say."

Ryan concedes, returning with Esposito a few minutes later with a large pile of papers.

"We printed out almost every thread, want us to help search through them?" Espo offers.

"Sure."

The four of them search through the posts, highlighting various areas that seem to match each girl's conversations with the killer. The pieces slowly come together, painting a portrait of their killer's taste.

"So, criteria: Lives in New York, has a wealth of knowledge regarding marine life, has visited various water sites in the city, is looking for people like her, and believes that she is a mermaid by various symptoms she exhibits," Rick recites off the list they've created.

"Okay, then, guess I'll start constructing an introductory post," Beckett states, fingers flying over the keyboard, her expression determined.

"Mermaid Beckett, I'm trying to picture it," Espo says, examining his colleague.

"I think you would look great in green and gold," Ryan chirps. Rick holds back a snicker.

"Nah man, red and black. Have a sexy little black seashell bra with a flaming red tail."

The author almost chokes, resisting the urge to inform Espo on how close he is to being right. In his peripheral vision, Beckett continues her assault on the keyboard, not even raising an eyebrow. Probably an effect of the boys' constantly ribbing one another, he muses.

"Ready to post," she announces a few minutes later, finger hovering over the mouse button.

"Wait," he interrupts. She stares impatiently. "Maybe I should look it over? Make sure it sounds good?"

"This is an online forum, not a publishing company," Esposito says. "Better for it to sound normal and not overly rehearsed."

Rick pouts, seeing the detective's point.

Beckett submits the posting before sitting back into her chair.

"Now I guess we wait," Ryan says, getting up. "Come on, Javi, I think I saw some leftover donuts from this morning in the break room."

The two disperse, leaving Beckett and Rick alone, again.

"How long do you think it'll take?" he asks.

"Don't know," she hums. "If he hasn't found anyone, and from the looks of these posts, he hasn't, he must be getting desperate, so it shouldn't take long."

He sighs, knowing that this part of the police work, the waiting. Doesn't mean he's going to like it.

"Why don't you go back to the boat and try to write? I'll let you know if anyone tries to contact me."

"Eager for my next book, Detective?" he teases.

"Hah!" She chuckles, eyes teasing. "No, just that we should probably spend some time apart. Don't need to weird out the boys."

Rolling his eyes, he rises from chair, giving her a wave as he departs. As he enters the elevator, he already begins feeling the loss of her presence. The mere thought forces him to lean against the lift, a small groan emanating from his lips.

He's screwed, and yet, he's fine with it.

* * *

It's a few hours later and he's in the middle of outlining a possible plot idea for his next book. He had wanted to stave off the idea that's been in his head, but unfortunately, sometimes he just has to embrace the muse.

The outline is coming along nicely, already reaching chapter ten, and the characters in his head are cooperating, forming a new universe.

He's so engrossed in his task that he almost doesn't hear the phone vibrate on the desk.

Snatching it up, his mouth forms into a grin at the image of Beckett on the profile picture. That was fast!

 _We got a hit. Was contacted by someone who sounds similar to merbuff. Guy wants me to meet with him some time during the week._

Rick frowns, finding it odd. The only time the killer and girls ever met was when he killed them. He voices the concern to Beckett.

 _I know, which is why I'm going to talk to him a bit more and then arrange a meeting. We're hoping he's just desperate and looking to gain my trust quickly. Come in tomorrow so we can figure out a game plan._

He beams, a thrill going through him at the sound of him being part of the team. Although, he's slightly disappointed that Beckett doesn't want to see him for the rest of the day. Oh well.

Her alter ego can keep him company.


	12. Chapter 12

AN: So here's the next one! Thanks to all the follows, favorites, and reviews for this story! I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 12

Rick strides into the precinct the next morning, rearing and ready to go.

"Look who's an eager beaver this morning," Beckett greets the minute she spots him, taking her daily coffee from his grip, examining him. "I continued talking to the guy last night and have a meeting set up for noon today. I just need the okay from the captain."

He nods as she walks into Montgomery's office. She's back a few moments later, a triumphant grin on her face.

"He says fine, as long as I have backup, of course."

'Where are you meeting him?"

"Near the Intrepid, actually. Ryan, Esposito,"

"And me," he interjects, knowing what she'll say.

Her lips quirk. "And you, will be nearby somewhere, listening to the conversation. Obviously, we're not expecting the guy to confess, but hopefully he somehow slips up. If not, I'll arrange another meeting and see what happens."

"All of which will end in you living."

She gives him a 'duh' look before going to her computer. "We have a couple hours to prep, so we should go over some stuff."

He nods in agreement and plops himself in his usual chair.

They discuss some of the research he'd done the day before, making sure she knows enough to have a conversation with their perp. It's no surprise she's a quick study and soon she's practically reciting the information back to him.

Two hours pass and Beckett's clearly had her fill of the aquatic life in the city.

"I'm going to go home and get ready for this thing," she announces. "I'll meet you guys there." He pouts and she rolls her eyes. "Gotta dress to impress." She winks.

"You already do," he tosses out, causing her to chuckle.

"Help the boys out while I'm gone," she instructs, before going to the elevator.

He watches her go, a bit miffed she didn't invite him along. His face must express as much because Esposito looks at him with pity.

"Dude, how long have you known each other?"

"A few weeks," Rick mumbles.

"Really? Because the way you look right now, I would say years." The detective shakes his head in disgust. "I haven't seen a guy become whipped so quickly."

"I am not 'whipped'." He so is. "I just find her very interesting."

"Whipped," Esposito repeats, returning to his desk.

"I think it's kind of cute," Ryan chimes. "However, it should go without saying, if you hurt her-"

"You guys will kill me," the author finishes.

"No, she'll kill you. We'll just help her hide the body," Esposito chirps.

Rick resists a shudder, instead giving a thumbs up in acknowledgment. They needn't worry though.

He cares about her too much to ever think of upsetting her.

* * *

Kate walks to Pier 86, her royal blue summer dress blowing with the light breeze, her white sandal heels maneuvering the wooden planks carefully.

"You guys ready?" she inquires as she approaches the boys. She holds back a smirk as Castle glances at her, his jaw dropping as his eyes roam her figure. While she might be dressing for this meeting, a small part of her may or may not have also wondered how Castle would react. From his heated gaze, it's clear her wardrobe choice is a success.

"Yep," Ryan answers, handing her the mic that will be used, as well as the earpiece. She hooks the mic to the chain of her necklace, and pops the other device in her ear. The mic is small enough that's it's covered by part of her dress. While Ryan and Espo fiddle with the radio that they'll hear her from, she adjusts the mic, leaning over slightly, giving Castle a quick flash at more of her cleavage. He bites his fist, earning a snicker from her.

"Alright, showtime," she mumbles, walking further down the pier, eyes scanning the area.

It's almost noon, so the guy should be arrive shortly.

She waits, making sure the Castle and her colleagues are in sight. The boys are relaxed, having done this before numerous times, but Castle is noticeably tense. While touched by his concern, he doesn't need to give them away. She motions with her hand for him to calm down. He nods, his shoulders relaxing, hands unclenching.

So, she waits. She begins to wonder if the guy got cold feet, but thankfully, her worries fade as a man who matches their killer's description approaches her.

"Hi…Alex?" she states, holding her hand out.

"That's me," he says, giving her a smile, returning the handshake. "So, Heather, was it? You're stunning!"

"Thank you. You're not so bad yourself," she replies. "So, what made you respond to my post so quickly?" Her tone is causal, innocent.

"You just seem like a very down to earth woman," he answers smoothly. However, unlike a certain author, the suave tone comes off as more sleazy.

"Why thank you." She twirls her hair with her finger, flicking it over her shoulder. "So, what made you join the site?"

He shrugs. "The same reason as everyone else, pretty much. I've always felt…different, but then I realized the signs matched the symptoms of being a you know, so I joined up."

She nods, pretending to buy his story. "I've pretty much felt the same way." It is partly true, in her teens years she had felt different, but she had always known that she was a mermaid, something her parents had informed her of as a young child. "I'm glad to find a community that's just like me. However, I don't think I'm as obsessed with it as the others."

As they begin to walk, Esposito informs her they'll follow her closely.

"Yeah, me neither, honestly," Alex replies, a wry smile on his lips. His green eyes glow with curiosity. "So, ah, what do you think of the boat?" He gestures toward the grand boat behind them.

"It's amazing, I've never been on it, however."

"Hmm," he hums, looking out into the water. "You're from New York, right?"

"Yes, why?" She cocks her head in confusion.

"Have you, uh, heard about the murders?" It's clearly supposed to sound offhanded, but Kate can tell it's an act. "Ya know, the women?" He glances at her, a nervous chuckle escaping him.

"Oh yeah, it's absolutely horrible. Their poor families must be devastated." She sighs.

"Yeah, and to think that they were members of the site," he says, his tone conveying dismay.

His statement causes her to stop and look at him.

"What makes you say that?" she asks.

"Well, that's what I read in the papers," he answers. However, she knows it's a lie. The NYPD hasn't released that piece of information yet. She thinks, trying to figure out what to say without blowing her cover.

"Oh, I don't remember reading that," she remarks.

"It must've been one of those online blogs." She can see him clenching his fists in her peripheral vision. They're further down the pier now, and there's less people around. "Or the forum, probably the forum."

'Well, at least the full moon isn't for a couple more weeks," she jokes, playing dumb.

"Right." He sticks his hands in his pockets, looking out onto the docks. "At least that one girl survived." They're now in the least populated area. He tilts his head. "Come over here." She frowns, following him cautiously to the edge of the pier that meets the water.

"Careful, Beckett." She hears Castle warn in her ear.

"What was her name? Jane Hull? Hill?" Alex furrows his eyebrows.

She's on high alert at this point. The NYPD never revealed the name of the survivor, thus forcing the media to refer to her as Jane Doe.

She keeps silent, but it must give her away because a dark chuckle escapes from her companion's lips.

"Did you really think I was that dumb?" he taunts, turning toward her. "Your messages oozed of desperation. It's almost quite amusing, the NYPD thinking they were outsmarting me."

"Fine then," she says, flashing her badge from the holster on her leg. "As long as we're being honest, Detective Kate Beckett, NYPD. Put your hands where I can see them."

He raises his hands without hesitation as the boys rush in, Castle throwing her the handcuffs. She recites the man's rights as people slowly come down to the pier to watch the show.

"Don't expect to keep me long, Detective," he snarks as she leads him to the car.

"I wouldn't be so sure about that." She opens the back door, pushing the guy inside, slamming the door shut with a loud bang.

"Well, that was easy," Castle remarks, lips pursed.

"A little too easy," she grumbles.

She has a feeling that their troubles have just begun.

* * *

'Alex' is thrown into Interrogation room three the minute they enter the Homicide floor. Rick stands on the other side of the glass, Beckett, who has changed into her suit from earlier, much to his disappointment, beside him. Their suspect appears unflustered, probably betting on his partner to bail him out.

"So, what do you think?" Rick asks her.

"I think it's time to get a confession out of this guy." She wastes no time in entering the room, power and confidence flowing off of her. Rick stares in awe, taking a seat at the table. "So, Alex," she starts, sitting, leaning across the table to the suspect, "what made you give up so easily? I thought a man of your cunning ability would try a little harder to hide."

Alex shrugs. "Maybe I was bored and I got tired of the chase. Or maybe it's because I know a lawyer's going to walk through the door in a matter of minutes and I won't have to say anything." He's smug, and Rick wants nothing more to punch this guy in the face.

"But why kill those women?" the author prods.

Alex snorts. "I'm not dumb. You guys figured out the mermaid part, I'm sure you know the rest. You know, if I did kill them." He leans back against the chair, the motion accompanied with the sound of his shoes scraping the floor.

"Come on, you really don't think it's possible, do you?" Beckett quizzes.

"Maybe it is, maybe it isn't," their perp retorts.

"I guess that part matters more to your partner, or boss rather," Beckett states, her voice dropping a tone. "He gives you nice sum, you two work together, find a girl, reel her in," Rick almost laughs at the unintentional pun, almost. "and then kill her for her supposed immortality." Her tone is mesmerizing, bordering on sultry. It's appealing, but strange. In fact, if Rick were on the other side of the table, he's certain he would confess without a second thought.

Alex opens his mouth to speak when the door flies open, a man with a briefcase charging into the room.

"Sorry, Detectives, but my client doesn't need to speak to you any longer," the man snaps, standing beside their suspect.

A cocky grin spreads across their suspect's face.

"He was pretty much confessing to me now," Beckett argues.

"From what I heard, it's all supposition and rhetorical questions. So, I highly suggest you find more evidence, otherwise you must release my client."

Rick notes that the lawyer never mentions their perp's name, meaning he's mostly likely in on the scheme.

The duo begins to leave the room, Beckett opening the door, when Alex says, "Also, nice trick, Detective. You almost had me, almost." He's still smirking, a knowing look in his eyes as he glances at her legs. She doesn't respond, exiting the room.

Ryan and Esposito, who have been standing behind the glass, glance at her in confusion.

"What was that about?" the Irish detective inquires. His colleague shrugs, shaking her head.

"I've seen that lawyer before, but I can't recall from where," Esposito mutters. "Eh, at least we have something to work on. Alex is definitely the guy, hypothetical or not."

"I'll look up the lawyer's name because I do recognize him too," Ryan states. "Maybe we can figure out this guy's partner that way."

"Well, let's get to it, then," Beckett instructs.

Once the boys leave the room, she bites her lip, seeming concerned.

"What's up?" he asks.

"Maybe I shouldn't have done the hypnotism thing," she murmurs.

"So you were doing that on purpose!" He stares at her expectantly. "More mermaid stuff?"

"Uh, yeah." She shakes her head. "I only do it when I'm really desperate to get a perp to crack, as a last resort. However, I'm afraid 'Alex' might have figured it out."

"You used your feminine wiles, so what?" Any guy would be charmed by Beckett. Then again, he may be a little biased.

She sighs. "When I showed him my badge, I think he may have seen my birthmark."

Birthmark? Then that means-

"Wait, so the crescent-shaped birthmark is a thing?" he blurts. "Why didn't I notice it before?"

Her lip turn upwards. "You were a little distracted."

Right. But who could blame him? She was nearly topless at the time.

"But, I just hope he doesn't catch on," she says.

"And if he does?"

She closes her eyes, running a hand through her hair.

"We'll just have to deal with it as best as we can." She opens her eyes, and they shine as she examines him. "Speaking of…would you be up for a midnight swim?"

Midnight swim? With Beckett? Did she really think he'd say no?

"Of course! What for?" he asks in an exuberant tone.

She rolls her eyes. "It's a surprise. I'll meet you where the boat's docked."

He pouts. "Not even a little hint?"

"Nope," she teases, popping the 'p'.

"Evil," he whines as she walks back into the bullpen.

Guess it's time to dig out his swim shorts.


	13. Chapter 13

AN: So, here's the next chapter! Thanks for all of the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 13

Kate waits for him by the docks next to the boat. It being midnight, most of the residents are in their homes sleeping, lights out. The only source of light remaining are a few safety beams farther out, but where she is now, it's dark.

She swishes her tail, making sure to keep herself hidden. The water feels nice, having absorbed the day sun. In fact, nighttime is her favorite time to swim, she can hide easier and the water isn't as cold. She recalls the times she had spied on Castle from a safe distance, and the one moment she dared to get closer to give him the seashell. The thought makes her smile, realizing how far they've come in just a few weeks.

As she muses, she hears the sound of a door opening from above her and the padding of feet on the dock.

"Beckett," Castle whispers into the darkness.

She flicks her tail, splashing around. He chuckles, walking toward the end of the dock.

"Nice bathing shorts," she remarks. Her heightened eyesight allows her to make out blue swim trunks, a pattern of cute various colored fish on them. It suits him.

"I wasn't planning on swimming much," he remarks, sliding into the water. He shivers briefly, clearly trying to adjust to the temperature. As he does so, her eyes roam his body, ogling his bare chest. While not overly muscular, he still has some build, and she resists the urge to run her fingertips down his abs.

"See something you like?" he teases.

She smirks. "Maybe. I know you do."

"Not going to deny it." Waggling his eyebrows, he asks, "So, where are we going?"

"I told you it's a surprise." A soft chuckle escapes her as he pouts. Such a little boy sometimes. "But, you do need to hold onto me."

She wraps her arms around his torso, indicating for him to replicate her actions. His arms, which are fairly strong, hold her close and she marvels at how well they seem to fit together.

"Oh wait, I almost forgot!"

She lets go, already missing his warmth, before cupping her hands in the water and placing them in front of him, near his face. She blows into the water, as if it's a balloon, and soon, a large ball forms around Castle's head.

"What is this?" he inquires, one hand poking at the air bubble.

"It holds in oxygen. Now, stop poking at it, you're going to need it." Her arms hold him once again, her tail in-between his legs.

"Anything else I need to know?"

She leans in, her lips ghosting the shell of his ear.

"Just hold on tight," she murmurs.

And then they're off.

* * *

He's flying. Or at least, he feels like he is. Beckett's swimming at the speed of light to wherever it is they're going. Everything's a blur as they pass, but the water becomes clearer and he's positive they're no longer in New York.

As they swim, he relishes in the sensation of her body pressed against his, it's incredible. He's never felt anything like it, even in his two marriages. He finds himself wishing that they never stop, just so he can touch her, feel her.

However, they do stop after some time. Beckett slows, before fully stopping and letting go of him. He doesn't fight the frown on his face.

"You okay?" she questions, concerned.

"Come back to me," he says, hands itching to pull her to him.

Rolling her eyes, she shakes her head. "You're fine then. Anyway, as cozy as that was," she says, her lips lifting into a gentle smile, "we should get going."

He follows and soon the water becomes much brighter. Staring ahead, his mouth gapes, eyes wide in awe at the large underwater city.

"Is that-"

"Atlantis? Yep," she replies, continuing toward the massive building.

"Wow," he breathes.

He's seen pictures over the years of what Atlantis might look like, the guesses from scientists and creativity of artists. However, none of it measures up to what he sees now.

They swim to a large stone complex that appears to shimmer. Its architecture is a mix of Greek and Roman white columns, each topped with gold spirals. As they move, Rick notices that the city is set up so that the buildings are connected to each other, all leading to the largest building, which he assumes is the palace.

He's admittedly a little disappointed when he sees no other mermaids around.

"Where is everyone?" he quizzes, searching for any other sign of life.

"Probably sleeping," she answers.

"Awwww." He was really hoping to see other merpeople.

"Trust me, you don't want to see others, or rather, you don't want them to see you." She turns, shrugging before stopping at what appears the city center. Various stalls are scattered in the area and shop signs hanging above doorways points to the space being the marketplace.

"Why?"

"You know how I would be considered, well, a freak up there?"

He opens his mouth to protest her description of herself, since she is far from a freak, but shuts it as she shakes her head. "Yes?"

"Well, it's kind of the same thing with humans here," she answers. "We may be half human, but mermaids who live down here don't see that."

He nods, sort of understanding the logic.

They swim to the entrance of the palace, coming across two guards with white and gold helmets guarding it. Both have green tails.

"Hello Demetrius and Nore," Beckett greets, nodding to them respectively. The first has blonde hair and blue eyes and the other has more orangish hair and striking green eyes.

"Hey Kate," Demetrius replies, beaming. "Come to see His Majesty?"

"Yes."

"Ooh, and you brought a human!" Nore exclaims. "He's not gonna like that. Is this the guy you won't stop talking about?"

"She won't stop talking about me?!" Rick grins, thrilled at the idea.

Her cheeks redden. "They're just teasing," she grumbles.

"Nah, she's been 'Castle this' and 'Castle that'."

Rick laughs, enjoying Beckett's embarrassment a bit too much. The guys actually remind him a little of Ryan and Esposito.

"Okay, okay, let's go."

She swims past the two, entering the grand palace.

He stares, eyes roaming the numerous displays of seashells, starfish, and other creatures on pedestals behind glass displays. The building surprisingly has ceiling, each section a dome lined with gold stripes and seaweed that descends and swirls onto the columns.

"How was this all made?" he asks.

"We do have hands," Beckett answers.

"Indeed we do," a male voice answers from another room. Beckett rolls her eyes as she swims through the doorway of what appears to be the throne room.

"Hello, King Mathias," she says, addressing a man sitting on a rock that resembles a throne. While not decorated with ornaments or jewels, the chair is still pretty imposing.

"Evening, Kate." His tone is warm, friendly. His eyes slide to Rick and he raises an eyebrow. "And I see you brought a friend from the surface." Mathias's expression remains unchanged, however, his tone carries an edge.

"Yes, this is Richard Castle, the man I was telling you about."

"The what did you call him? Nine year old on a sugar rush?" The king floats down to them, examining the author, who now has a an up close view of the creature's grey, beady eyes.

"Hey!" Rick objects.

"Why is he down here?"

As Mathias interrogates, Rick feels a sharp object poking his thigh. It's then that he realizes the mer-King holds a trident in his hand, a very sharp, shiny trident.

"He can be trusted, Your Majesty." Beckett places herself between the two, steering Rick clear of the weapon.

"Is that your head talking, or your heart?" the merman prods. She glares and the merman purses his lips. "That's what I thought."

Her heart? Wait, does that mean-

"He can be trusted! He won't say anything, I promise!" she says, her voice close to begging.

"I promise," Rick interrupts. "I won't tell a soul about any of this. I wouldn't want to put Beckett at risk in any way."

The king scrutinizes the writer, grey hair flowing behind him. "Do you know how many have said that over the centuries and then turned around and betrayed us?"

"I won't do that to her," Rick answers with conviction. "I couldn't do that to her. I lo- care about her very much."

He sees Beckett's eyes flash with realization, but doesn't comment. They can discuss that tidbit later.

"Hah!" the King scoffs, his orange tail flicking in agitation. "That feeling is an illusion to you humans, you only think you do. You would say that about any merperson you came across."

Rick, now furious, gets into the king's face.

"Beckett is a remarkable, maybe even a little maddening, woman. I feel privileged that she let me follow her on her case and quite frankly, I'm hoping to have a long standing relationship with her after the case is over." He huffs, not even caring if he's freaking Beckett out a little. It's out in the open now and he just hopes that she doesn't try to push him away again.

Mathias looks at him, an amused smile on the king's lips. "I have to admit, you're much more convincing than other humans. But the question is, will you live up to your promise?"

"Guess you'll have to find out," Rick replies, pulling Beckett to his side.

She huffs, gently pushing away from him.

"Anyway, now that you've gotten that out of your system," she mutters. "I came to discuss what we've found in our case so far."

"So tell me," the King says.

Beckett relays all of the information of the last few days, the king nodding along occasionally. Whe she's finished, Mathias sighs.

"So, do you think you will catch him soon?" the king inquires.

"I'm hoping my colleagues find out who the lawyer works for, then it shouldn't be hard to find the culprit."

"I really wish you can," the merman mutters. "It would not be good for us if they found any of our villages, let alone Atlantis."

"I know," Beckett replies. "Anyway, we need to get going."

"Goodbye, Kate." The king nods to the author. "Goodbye, Rick. And remember what I said." He raises an eyebrow, a small smile playing on his lips.

"Your secret's safe with me," Rick replies.

Mathias dismisses them with a wave of his hand and the two swim out of the palace.

"Well, that was interesting," Rick mutters as they travel the city center again.

Beckett shrugs. "He means well, just trying to protect his people. But yeah, he can get a little intense sometimes. You should've seen him when I first told him what was going on."

Rick shudders, easily picturing the merman enraged.

"Do you report to him?"

"Only on occasion, just so he knows that merpeople are safe to go the surface. Obviously, I've been doing it more often lately."

He hums in acknowledgment, admiring the scenery around them. Beautifully colored corals and marine life surround the duo as they swim to what appears to be the outskirts of the city.

"Come on, I want to show you something," Beckett says, gesturing for him to follow her.

"Are you taking to me to where all your human gadgets are?" he jokes. All he receives is a snort. He chuckles.

It was worth a try.

* * *

Soon, they reach a small grotto and enter, Beckett indicating for him to sit, or attempt to, on a rock that serves double as a seat. As he does so, Rick notes various pictures on the walls, similar to primitive cave paintings.

"Mom used to take me here as a child," she starts, gazing at one of the drawings. "'Never forget where you're from, Katie' she would tell me." Her fingertips trace another picture, her tail slanting in what seems to be melancholy. "These pictures illustrate some of our history and folklore. I have no idea who made them."

He moves next to her, examining the inscription. It looks like a mermaid swimming to the surface.

"It's weird because she was half human herself." Huh? Aren't they all half human? As if reading his mind, she answers, "I mean genetics wise. Her mom was mermaid and her dad was a human. My father's parents were both merpeople."

"Interesting," he murmurs, looking at the other pictures. "Do you come here often?"

"Not so much anymore." She swims closer to him, to the point where they're almost touching. "It hurts to be here sometimes, without her." As she faces him, a slight smile forms on her face. "You being here makes it a little easier."

"I'm glad," he answers, drawing her to him. "I mean what I said to Mathias before, I plan on being around."

Wrapping an arm around his waist, she murmurs, "I know."

She leans, her face close to his. "I would love to kiss you, but I don't want to burst your bubble, literally."

They laugh, and a charming smile spreads across his face.

"Then, why don't we go up to the surface so that you can?" His tone is suave, but she just chuckles and rolls her eyes.

"Alright then."

She holds him tight and as he reciprocates, he resists the urge to lean her head on his chest. She begins to swim upward, careful not to go too fast.

He's never felt happier.


	14. Chapter 14

AN: Here's the next one! Thanks for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 14

They resurface a while later, popping up to the dock by his boat.

"Well, that was exhilarating," he remarks, trying to adjust himself to the fresh oxygen since his bubble has popped.

"I've never taken a human on a speed swim," Kate responds as he climbs onto the dock. "So, I don't know what happens. You feel okay?"

"I'm fine," he replies, and he is fine. More than fine actually. He's been pressed up against Beckett for a good while, so he's happy as a clam.

"So, I'll see you tomorrow," she says.

He glances around, noting that it's pitch black It's most likely almost three o'clock in the morning, so everyone is in his or her home.

"Why don't you stay with me?" he offers. "It's late and it'll probably take a while for you to get home."

She purses her lips. "You sure? I don't want to be an imposition."

"You won't be," he insists. He eyes her, realizing that regardless of arm strength, getting to his boat is going to be an issue. "I'll be right back."

Going onto the boat, he rummages around the front closet, and returns with a large towel.

"I'll carry you in." He holds out the cloth and Beckett shakes her head.

"You don't need to do that."

"Do you want splinters in your arms?" he retorts. Her lips form into a cute scowl as she takes the towel and places it on the wooden planks.

"You just want an excuse to hold me again," she teases, pulling herself up and wrapping the material around her tail.

"I won't deny that," he chirps.

He lifts her up, finding her to be light as a feather. He's careful to ensure no one else is around before taking her to the boat deck.

"I don't have anything to sleep in," she grumbles.

"You can borrow my stuff. I'm sure I have a t shirt that's plenty big. Also, I'll throw your clothes in the dryer."

"You have a dryer?"

"Yep." The elderly couple has plumbing in their boat, so they have a washer and dryer, which makes things much easier for Rick on the hygiene end.

Once he escorts her inside, he deposits her on the couch, letting her dry off her tail. Soon, she morphs back into her human form, which leaves her in a light blue t-shirt and jeans.

"No shoes?"

She shrugs. "I left them where I took off from earlier."

He nods before entering his bedroom and pulling out a t-shirt and a pair of boxers.

"Here you go." She shoots him grateful look before going into the bedroom. While a little disappointed, he knows there not at that level, yet.

Returning a few moments later, she smiles, pirouetting in front of him.

"So, how do I look?" she jokes, hands on her hips.

"Absolutely divine," he murmurs, eyes roaming her frame. Beckett in his clothes is one of the sexiest things he's ever seen.

The shirt is an old navy blue thing he keeps for sleep wear. The piece of clothing goes down to her mid thigh, almost flowing. There's a hint of the black boxer peeking out from underneath the shirt. To add to that, her hair is adorably tossed. He takes in the sight, committing it to memory.

Reaching his hand out, he invites her to step closer and she obliges. Tugging her to him, he places his chin on the top of her head.

"I believe I promised a kiss," she states, voice muffled by his chest.

He chuckles. "Indeed you did."

Tilting her head up, he grins before gently placing his lips against hers. She reciprocates, their kiss becoming more passionate each second.

He leads her to the couch, pressing her body up against it, relishing in the soft moans that escape her lips in-between as he moves to her neck. Before they go any further, however, he's somehow able to restrain himself.

"As much as I would love to continue this," he breathes into her neck. "I would much prefer to do this in my very spacious loft." His hands trail down her torso, stopping at her hip, his fingers tapping the small indent in her back. "In my very spacious bed, where I can explore every inch of you without any type of hindrance."

She releases a small whine, but seems to agree as she pulls back from him. Resting her forehead against his, she smiles softly.

"I think that might be a good idea," she mumbles. Straightening herself up, she stands, grinning. "Well, good night, Castle."

"Until tomorrow, Beckett," he answers, gesturing for her to go to the bedroom. She's about to protest, but seems to think better of it. Good.

Once she's off, he lays himself down on the couch, adjusting himself until he's as comfortable as possible.

Soon, he drifts off to sleep, dreaming of the woman in the next room.

* * *

Kate wakes the next morning, the scent of pancakes, chocolate chip to be exact, and her favorite coffee, hitting her nose. She sits up, remembering she's not in her own bedroom.

She glances at the desk next to the bed and she spots her clothes from the previous night. A wide smile stretches across her face, and she bites her lip. Castle can be so sweet.

Throwing her clothes on, she looks at the clock on the nightstand, seeing it's still fairly early. She swears, realizing her phone is at home. Hopefully no one's been looking for her.

She saunters into the main area of the boat, which is a living room and a very small kitchenette. Her thoughts briefly wander to how Castle is able to stand the small space, given his height. Guilt courses through her at the thought of how uncomfortable he must've been sleeping on the couch. She'll definitely make up for it, soon.

"Morning, my dear detective," he greets as he places a stack of pancakes on a plate. "I figured you'd be up early." He pushes the plate toward her at the table, indicating for her to eat.

"Thanks, Castle. You didn't have to do this." She sits, licking her lips at the delectable looking food. It has been a while since she's had pancakes.

"Nonsense." As a mug appears in front of her, her eyes widen at the heart shaped foam in the middle of the beverage. "Just a little something for your morning."

"Thank you, really." Sipping, a contented sigh escapes her. Whatever he does to the coffee, it's heavenly.

"So, Ryan and Esposito texted, said they couldn't get a hold of you." He raises an eyebrow.

Great. "I left my phone at home. What did they say?"

"They might have figured out who that lawyer works for. They wanted you to come in and just corroborate the information with them."

Relief fills her as it seems the case might finally be coming to an end.

"Did they say who?"

He shakes his head. "No, must be someone big if they won't say over a text."

She nods, taking another bite of her pancakes. "I need to go home first and change and grab my phone."

"I'll drive you because as I recall you don't have any shoes."

Right. "Okay then." She knows there no use in protesting.

He looks a little too satisfied, a smirk on his face, one she wishes to kiss off. She'll do it, later.

Once she's finished and they both clean up, they head out to her apartment, Castle at the wheel. She hates other people driving, but for him, she'll make an exception. She pouts, noticing how lenient she's become lately. Stupid mermaid influences.

"Everything okay, Beckett?" he inquires.

"Yep," she replies. "Just eager to close this case."

"Same here. The sooner we catch this guy, the sooner there's one less potential death."

She nods, grateful that they're on the same wavelength in regard to justice. Though, they're in sync about many things. It's remarkable.

When they reach her building, she exits and tells him to stay in the car.

"I'll meet you at the precinct."

"Afraid to be seen with me?" he asks good-naturedly, eyes twinkling.

She rolls her eyes. "No, just need some time to myself." She may like him, but she still needs some time alone to think.

He tosses her a wry smile, understanding. "I'll see you then."

Giving her a little wave, he drives away.

She walks into her building, ignoring the stares of people who notice her bare feet.

At least she has clothes on.

* * *

She walks into the precinct about an hour and a half later. Castle's already sitting in his accustomed chair when she arrives at her desk.

"Yo, Beckett," Esposito announces, striding toward them. "We think we have a hit on who this Alex guy is working for." He holds out the iPad, letting her browse the information. As she reads, her eyebrows raise, lips pursed.

"You sure about this?" She peers at him and Ryan, both appearing certain.

"Yeah, it took us a while to remember where we saw that lawyer, but then we realized he was from those press conferences a few years back that dealt with those bribery allegations in District Attorney's Office."

"The ones where the ADAs were supposedly bribing the judges in some cases?" Castle asks.

"Yeah, those ones," Beckett responds. "What does that have to do with this?"

"Well, this guy has been there since the eighties, and was hired by then DA, and now senator, William Bracken, who has his own skeletons."

"Okay and?" She knows full well about Bracken's supposed skeletons. Her mother and father weren't fans of him and her mom didn't trust the former DA.

"That aside, he seems to have a high interest in marine life. Been to a lot of the grand openings for aquatic stuff around the city. Also, he's partnered with some of the diving centers to expand the areas in which citizens can dive around the city," Ryan says, appearing surprised. "Who knew the guy was into that type of stuff?"

"Huh," Castle remarks, glancing at her. She knows what he's thinking and she agrees. Thankfully, no one's found any of the colonies. "Have any old pictures of him?"

She performs a quick search of Bracken and finds several old pictures, most of them comparing him to what the senator looks like now, which isn't much different. His face is still full of youth from over twenty years ago, not a wrinkle or gray hair in sight.

"Wow, he must have a really good plastic surgeon and stylist," Espo jokes. However, the images make her stomach turn and she sees horror in Castle's own expression.

"Er, yeah." A nervous chuckle emanates from her lips. "So, maybe we should pay him a visit?"

"Right," Ryan says. "Would you rather us go? If Alex has warned him, seeing you two might spook him."

She bites her lip, unsure. She wants to bring this guy in herself, craves it, but she knows it would be more practical to send Ryan and Espo.

"Okay yeah, you guys go. Bracken has a local office nearby. See if you can get in and question him."

The two boys leave, eagerness radiating off both of them.

"How many do you think he-" Castle starts to ask, but she shakes her head.

"I don't know, I've only heard stories. It's said one mermaid alone could sustain someone for several years." It's supposed to be old folklore, something to keep the merchildren from swimming up to the surface. Now, she's not so sure.

"So, why the screw ups? I mean, if he's done this before, why are there errors?"

She sighs. "The website is probably more of an experiment. Who knows? Maybe with enough misses he'd stop using it. But then he'd move on to something else."

Castle nods, thinking. "I think I have a feeling of the answer, but out of curiosity, how is the immortality gained?"

"The seeker is supposed to kill the merperson and extract some of their blood during the full moon and inject it, or drink it, or something. I don't know the exact details, but it's pretty brutal for the merperson."

"Wait, I thought you couldn't get hurt?" His eyebrows furrow in confusion and she shrugs.

"There's something about the full moon that makes us weaker, more susceptible to attack. So, yeah, we can die on a full moon." She's never paid much attention to the old tales, just what her parents told her as a child. Detachment has always been key with her when it came to the underwater world, with the exception of the occasional report to Mathias. However, now she's starting to question her choices with remaining separated from that part of her life since her mom died.

"We have what, another week and a half? So, hopefully, this guy caves, if it is him."

"Given how far this has gone, I don't think so."

"You can charm him," he jokes. She snorts, shaking her head. That was such a stupid move and she's positive Alex caught on to what she was doing. "Alright, anything we need to do in the meantime?"

"No, not really. We've gone through everything we can and as far as we know, Alex is in the wind, for now." She hates these moments, where there's a dead end and not much to do. "We just have to wait for Ryan and Esposito to return. I do have paperwork to do."

Castle pouts, of course, but remains in his seat nonetheless. Whipping out his phone, he plays whatever the latest game is now, leaving her to concentrate on work.

Time passes and the boys still haven't returned.

"Where are they?" she mutters, sending a text to Espo. He responds back quickly.

 _The senator is taking his precious time meeting with us. We're apparently next in line._

Of course. Bracken is most likely taking a power trip.

"Looks like they're stuck," she grumbles to Castle.

"Even I don't think I could get in," he offers. "I have friends in high places, just not that high."

She just shakes her head, returning to the file in front of her.

After another hour and a half, the boys finally return, each wearing a disappointed expression.

"I'm assuming it didn't go well," Castle surmises.

"The guy all but laughed in our faces," Esposito grouses.

"Yeah, 'How dare you question me. I'm a main pillar of this community. What an asinine thing to accuse me of.'" Ryan mocks.

"Great." Kate runs a hand through her hair. "So we have nothing, absolutely nothing."

"Oh, not exactly nothing," Espo chirps. "He took a call when we left, from the lawyer."

"Hear anything interesting?" she quizzes.

"A lot of the conversation was along the lines of something getting taken care of soon," Ryan answers.

She slumps her shoulder in dejection, wishing to bang her head on the desk.

"Sorry, boss," Esposito apologizes.

Waving a dismissive hand, she sighs. "It's okay, we'll figure something out." What it is, she doesn't know.

"Hey, why don't I go on a coffee run, cheer everyone up?" Castle offers. It make her smile, knowing that he wants to boost morale. He may have only been there a few weeks but he does feel like part of team.

They give him their orders and he leaves, but not before asking Captain Montgomery if he wants anything.

"I'll miss him when he's gone," Espo says.

"What do you mean when he's gone?" Beckett demands.

"Come on, do you really think he'll stick around? I mean he's interested in you, sure, but this has to be boring him."

Taking a deep breath, she tries to calm herself. He wasn't there when Castle made his promise last night.

"You never know, he might stick around," she hedges.

"I like him, I'm hoping he stays," Ryan chimes.

"You two are something else," Esposito says, shaking his head in dismay before reoccupying his desk.

"Don't worry about him, Beckett. I'm sure he'll warm to Castle, eventually."

She lifts her shoulders, eyes glancing at the paperwork. Even if Espo doesn't begin to like Castle, it's not like he has the final word of the author around.

"Well, let's get back to work," she states, contemplating on what to do next.

As she ponders, she notices her head start to hurt. Huh, weird, she never has headaches. One of the perks of being a mythical creature. She brushes it off, filling out another form.

As she reads, the pain in her head grows, almost throbbing. Her fingertips reach up to her temple, massaging it in hopes of relieving the pain. No such luck.

"Hey, you okay, Beckett?" Ryan inquires.

"Yeah, you don't look so good," Espo comments.

"I'm fine, just a migraine." She grits her teeth. What the hell is going on?

"Maybe the coffee will help. Speaking of, where is Castle? He's been gone for a while" Espo frowns.

She realizes he's right. Castle doesn't take that long to get stuff from the little cafe on the corner, unless he's become side-tracked.

She sends him a brief text, expecting a reply in minutes. However, nothing comes.

"Maybe he went home," Ryan jokes, earning a glare from her. "Sorry."

The pain in her head hasn't subsided, but it hasn't grown worse either. As she tries to alleviate the ache, she realizes that the feeling is similar to having been hit by a blunt object.

"Any answer?" Espo questions.

"No," she grumbles, staring at her phone forlornly. Something's up and she doesn't like it, not one bit. She starts to text him again when the phone pings.

 _Check your email, Detective._

Her stomach turns at the sentence and she immediately clicks into her email, finding one new message without a subject.

The content of the message is just a grainy video, featuring an all too familiar face.

"Castle," she breathes, heart dropping at the image. He's tied to a chair, blood oozing out of his head. Well, that explains the headache.

The one fact about mermaids she knows is true is when someone's soulmate becomes hurt, their significant other feels it to some degree. When her mother was murdered, her father started feeling pains in his abdomen while they were at the restaurant. He had tried to hide it, but she had known something wasn't right.

"Shit," Esposito swears.

"Hello, Detectives," a recognizable voice greets from behind the camera. "As you can see, I have that writer of yours. Bit of struggle grabbing him, but I have him now."

She clenches her teeth, hands curling into fists. Alex continues, each word filling her with disgust.

"If you want him back, you are to allow Detective Beckett to come alone, tonight at nine o'clock."

"Like hell," Ryan states. She hushes him, hanging on the kidnapper's words.

"You are to come where we met yesterday, understood?" Alex lets out a low chuckle. "Until then, I think I'll enjoy getting to know Mr. Castle a little better."

Alex comes into the screen's view and the sound of something scraping across the floor fills her ears. If she could become ill, she would. It's a tub, probably filed with ice cold water.

"Don't listen to him, Beckett," Castle pleads.

Alex whacks him with the butt of a gun, and she cringes, feeling some of the impact herself.

"I'll see you then." The kidnapper chuckles darkly before the screen goes black.

She about to see if she can track the email, but sees the address is a throwaway, the kind that would be used on the deep web, according to Castle.

"No, no, no," she mumbles.

"Come on, Beckett. We'll find him," Espo coaxes. "Let's go talk to the captain and see what we can do in terms of backup."

"No," she says, shaking her head.

"No? You're not seriously thinking of going alone, are you?" Ryan prods.

"Not alone, but I need to meet this guy face to face."

"I wonder why he wants you specifically?" Espo wonders.

"I, uh, don't know," she mutters, lying through her teeth. "Anyway, we still have quite a few hours until I see Alex. Let's find out if we can get any clues from the video about where Castle's being held."

They start the video again and she tries to concentrate, searching for any type of window or sign or anything to help indicate where Castle is located. However, the pain in her head hinders her focus and she's starting to feel a heaviness in her chest, like there's water in it. It won't actually harm her, but it still hurts. It pains her, both literally and figuratively, to know what Castle is going through right now.

"Do you want to sit this one out?" Espo questions.

"No," she grits out, gripping the desk. She sure as hell isn't going to stand on the sidelines as the man she cares about is put in harm's way.

Alex will have hell to pay.


	15. Chapter 15

AN: So here's the next one! Thanks for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 15

Rick watches as Alex cuts the filming, turning back to the author.

"Let's have a little chat, shall we?" his kidnapper inquires, looming over Rick. Rick's gaze shifts to the bucket, knowing it's going to be more than a 'little chat'.

"Great weather we're having, right?" Rick jokes. The kidnapper's lips twitch before rolling his eyes.

"Let's talk about your case," Alex starts, going behind Rick and undoing the handcuffs around his wrists, his legs remain tied to the chair. He pushes the man's body forward, re-cuffing Rick's hands behind his back.

"What's there to talk about? You seemed to know enough about it when we interrogated you?" Rick quizzes.

"Yes, I know most of it, but apparently I missed one crucial thing," Alex states, grabbing the collar of Rick's shirt. "Tell me, what do you know about Detective Beckett?"

Shit.

Rick shrugs as best he can. "Not much, I've only known her for a few weeks."

Alex shakes his head. "And I think you're lying. Do it again and your head goes underwater." The man pushes Rick forward, his face inches from the ice cold water. "So, I'll ask again, what do you know about Detective Beckett?"

Rick rolls his eyes. "I"m sure you already know her history, with you being one step ahead of us and all." He's going to try to mess with Alex as much as possible, even if it gets his head dunked.

"Oh yes, I know all about her tragic past and why behind she became a cop. I'm looking more for the woman behind all that, shall we say." Alex tightens his grip not he fabric. "So, what do you know about her?"

"I know she likes coffee," Rick jokes. A second later, his face hits the water and he's gasping for air, the ice cubes hitting his face as he struggles to breathe. He's allowed back up a few moments later, his lungs beginning to burn.

"Let me make this easier for you," Alex growls. "I'm going to assume, that being a cop, Detective Beckett is very much a skeptic. And that something like this type of case would have her scoffing. According to my sources, you were the one with the major breakthrough in the case, the one to bring up the mermaid and immortality factors. How did you convince her that was the motive?"

"Well, she knows there's enough loons out there to believe that stuff," the author lies. His head receives another dive, staying under for a little longer.

Alex makes a clicking sound with his tongue. "You're trying my patience, Mr. Castle. Why did she really think it was that? She wouldn't listen to an outsider like you, unless she already thought that was a possible motive."

"Well, I don't know why she would've thought that before hand," Rick snarks. His face meets cold once again. Now, his lungs are on fire, every other breath becoming a struggle.

"Do I really need to spell it out for you?" Alex reaches over to a table, shoving some photos in Rick's face. The author's eye widen in horror when realizes that they're pictures of Kate throughout various times of the day. "I've been following her movements lately and have had several instances of her returning to her building soaking wet."

"Maybe she takes showers at the precinct?"

"Please, at midnight? I don't think so." The kidnapper purses his lips, leaning his face near Rick's. "Plus, her little interrogation trick caught my eye as well, as well as her birthmark she accidentally revealed when showing me her badge. So, I'm going to ask, is Detective Beckett a mermaid?"

Rick glares. "I don't know."

His head goes underwater again, this time for longer. When he resurfaces, he's gasping for air.

"I'm going to give you another chance to answer the question. So, yes or no?"

"No!" Rick hisses defiantly.

"Liar!"

Rick is underwater again and he's unsure for how long it is this time. When he's forced back up, spots cloud his vision and he breathing is almost nonexistent.

"I'm going to leave alone for a bit, maybe you'll cooperate when I come back?"

"You're not going to kill me?" Rick manages to force the words past his lips.

Alex smirks. "Why would I? Your lovely detective would have nothing to run to then." With that, he steps on a ladder, opening a hatch above them, allowing some light to filter through and taking the ladder with him once he's on the deck. A second later, Rick's left in darkness, cold and alone.

He prays Beckett and the boys find him soon.

* * *

Kate bites her lip, discreetly taking a breath. If her lungs are anything to go by, Alex has apparently stopped torturing Castle, for the time being. She's relieved he's gotten some reprieve, but for how long?

She and the boys have been going through the video, attempting to find an ounce of clues as to where Castle is being held. So far, nothing.

"Play it again," she demands to Ryan, who sighs.

"Look, Beckett, we've seen this video numerous times now," he answers.

"Again," she insists, finally able to concentrate.

They play it once more, searching. The main issue is the poor lighting, almost dark, so very little detail is apparent at first glance. She examines the background, looking for something, anything, trying to ignore the torture scene as best she can. When the film is almost over, she finally sees it.

"There!" she exclaims, pointing to the upper right corner of the screen.

"What is it?" Espo asks, squinting.

"It's a hatch," she explains. "Like one you find on a boat!"

"Hmm. Do you like he took Castle out to the river?" Ryan asks.

"My guess would be no. Not if he wants to meet me," she murmurs. "Let's see if we can find out if anyone boarded a boat recently, or at least asked to borrow one."

"We'll start calling the piers and boatyards," Ryan says. Him and Esposito go to work, while she starts making her own phone calls.

About halfway through, and still no luck, Captain Montgomery interrupts her, requesting her in his office.

"Yes, Sir?" she quizzes, following his gesturing to shut the door.

"Do you need to step away from this?" he asks, no judgement in his tone, just concern.

Shaking her head, she answers, "No." There's no way she's backing down.

"Really? Because you look like hell." She school's her features and he continues, "If this is too personal for you, perhaps you need to go home for the day." He raises an eyebrow.

"I'm fine, Sir. I fully intend to bring this guy in, particularly since he made the mistake of taking one of our own."

She swears Montgomery smiles, but it's gone in a flash.

"Fine, but please keep me up to date."

She nods and turns to leave when Esposito barges in.

"Sorry, Capt'n, but we got a hit. Some guy rented a boat earlier today, said he needed for two or three days. Guess where it is?"

"Pier 86," Kate guesses.

"Bingo!"

"Good. I want you to bring backup, understood? Bring surveillance if needed," the captain instructs.

The detectives agree before leaving, preparing themselves. Adrenaline pumps through Kate's veins as she grabs her piece, placing it in her holster. Her thoughts move to Castle, and she sighs, hoping that he's still okay when they find him.

 _Hang on, Castle, we're coming!_

* * *

They reach the pier about a half hour later, well before the meeting time with Alex. However, the detectives could care less as they set up in the unassuming van.

"So, ready?" Ryan asks as Beckett preps herself with an earpiece and mic.

"Yep," she answers, looking over the boat information once again.

"Good luck!" Espo calls as she exits the vehicle.

She takes a deep breath, walking toward the boats. She mentally tunes herself to the conversation ahead. The plan is to get Castle and get out. She hopes it goes smoothly, but doubts it will.

As she makes her way toward the boat, she discovers to her dismay that it is the farthest and only vessel occupying the end of dock. She slowly approaches, seeing Alex on the deck.

"Careful, Beckett," Esposito warns as she stands in front of the boat.

Alex looks up from whatever the hell he's doing, and smirks.

"Well, well, what a surprise," he snarks. "I figured you couldn't wait to see me."

"Where's Castle?" she demands.

"Oh, he's fine, Detective. A little wet, but fine." Alex taps his foot on the deck making clear indication of where the writer is located currently.

"I want to see him," she answers.

The kidnapper rolls his eyes in exasperation. Opening the door, he gestures for her to peer in. She cautiously steps forward, anger fueling her when she sees Castle restrained to the chair.

"Beckett!" he calls, voice hoarse, tossing her a weak smile.

"See? He's fine. But you already knew that, didn't you?" Alex sneers.

"What's he talking about?" Ryan asks. She ignores it.

Backing up, Alex pulls out a gun, pointing it at the hatch.

"Now, here's what's going to happen: You're going to leave your gun here and come with me. Otherwise, the writer gets a bullet lodged in his brain."

"What do you want?" she asks, but she has a feeling she already knows.

"I want you to show me the colonies," Alex snaps. "You most likely know where they are. Oh, and don't worry, Mr. Castle was very loyal. Never said a word."

She grits her teeth, receiving a barrage of confusion from the earpiece.

"Come on, Detective, I'm waiting," he chides before adding, "Take out the earpiece and mic too."

She closes her eyes, her brain running through all the possible scenarios. The van is too far for back up to rush in and while she has her gun, she doesn't want any moves to end with Castle dead.

"Okay, I'll go," she says, removing her gun from the holster and placing it on the dock. She does the same with the mic and earpiece, turning around, holding her hands up.

"Good," Alex chirps malevolently, producing a knife from his pocket and cutting the rope securing the boat to the post. "Now, turn around, hands behind your back."

She growls, but complies, feeling and hearing the sound of zip-ties binding her wrists together.

"Go in," Alex barks, gesturing for her to join Castle. She obeys, letting him shove her down, immediately standing next to Castle once she's inside, checking him over. "Buckle in." Alex throws a lantern down, snickering. With that, the hatch slams closed, living the duo in semi-darkness.

"Are you okay?" she asks as her eyes adjust to the low lighting.

"Cold, but otherwise I'm fine," Castle murmurs.

"He waterboarded you," she hisses.

He shrugs. "No big deal." She can tell he's lying. "You?"

"I'm fine, now that I know you're okay." She beings to search, looking for a way to undo their bindings.

"What did he mean by you already knew I was fine?"

She hesitates, but explains to him what happens with mermaids and soulmates.

"So I'm your soulmate," he murmurs in awe. She smiles. "Not the best time to learn that, but it's great to know."

"Yeah, well, if we don't get out of here, we won't be able to explore that tidbit."

Glancing at the lantern, she kicks it, hard, making it slide across the floor and crash into the wall, shattering the glass around the bulb.

"I think I found how to free ourselves," she says.

"Too easy," he says and she nods in agreement. "Plus, I have these." He shows off the cuffs.

"Well, if Alex is expecting us to do this, why not play along?" she suggests, sitting down and beginning to saw at the binds.

"You have a plan?" he asks excitedly, grinning.

"I think so," she mumbles. "So, here's my idea…"

He listens intently, interjecting on occasion and making suggestions. As they hash out the details, she smiles, enjoying how in sync they are, knowing that their teamwork is vital and that he has her back.

The son of a bitch is going down!


	16. Chapter 16

AN: Here's the next chapter! Thanks for the follows, favorites, and reviews for this story. I really appreciate them.

Disclaimer: I don't own Castle.

* * *

Chapter 16

"Finally!" Beckett exclaims triumphantly, standing up and spreading her arms out. "Took a little longer than I thought."

Rick smiles as she walks over to him, carefully examining his face.

"You're bleeding," she murmurs, fingers grazing over the open wound on the side of his head.  
Her hand goes for the tub and he raises an eyebrow.

"Should you be doing that?" he quizzes and she shrugs.

The water floats, touching the injury and he can't hold back the shiver it creates. She gives him an apologetic glance as she chants, healing. A second later, his head feels much better, the throbbing gone.

"Thanks," he says.

Nodding, she grips the piece of glass and begins to cut his legs free of the ropes. As soon as she finishes, the hatch above opens, revealing Alex with his gun, again.

"You," he barks to Beckett, "Up here."

She glances at Rick, who's still sitting in the chair, attempting to fill her eyes with reassurance as Alex tosses the ladder down. She gives Rick a quick hug before heading up. When she reaches the deck, Rick can hear the two speak in low murmurs, but can't hear what's being said. But he's pretty sure he already knows.

Soon, the hatch closes again and the author sighs in relief. Standing up, he stretches his legs before picking up the piece of wire Beckett dropped while giving him the hug. He snickers, picking the lock of the cuffs. It takes a bit, but the cuffs eventually fall from his wrists.

"There we go," he murmurs to himself, rubbing his wrists for circulation. As he does so, he listens carefully, making sure there's no one on deck before climbing up the ladder and pushing the door open. Thankfully, Beckett had been able to distract their kidnapper long enough for Alex to forget about that piece of equipment.

As Rick reaches the deck, he smirks when he sees traces of diver equipment, such as tanks and flippers, scattered around the edge of the boat, along with Beckett's shoes.

Good girl, he thinks, a goofy grin forming on his face.

Their plan, as far as he can tell, is going smoothly. However, he needs to fulfill his part in order for it to succeed.

Eyes scanning the boat, he searches for the communication area, which he finds a level above the deck. Approaching the small hub, he's not surprised in the least to see no GPS system.

"That would be too easy," he grumbles.

Thankfully, however, there's a map on a bulletin board, where Rick can sort of make out coordinates for their location, since Beckett was able to say where they most likely were in relation to the colonies.

He reaches for the radio, ready to call in an S.O.S for them when he realizes something.

"Shit," he swears, messing with the dials and switches. However, he can't seem to bring the communication system to life. He huffs, shaking his head in dismay, holding the silent radio.

Now what?

* * *

Kate swims several yards from the boat, feeling Alex close behind her, his presence looming. She's tempted to ditch him, but doesn't want to him to go back to the boat and harm Castle. So, she leads him on.

At one point, she turns, glaring and pointing a finger.

"Remember what I told you, hands off," she orders, recalling the look of absolute lust that had crossed the killer's face when she had transformed.

"Yeah, yeah." He waves a dismissive hand.

She huffs before going under, waiting for him to put his scuba mask on. She refrains from smirking when he appears underwater, well equipped with diving gear.

"Lead the way," he barks and she obliges, traversing through several rock and plant formations, her brain slowly recalling the path.

"Just to warn you, it's been a while since I've been here," she says as they journey along. She hasn't visited either of the colonies in years. She just about remembers where they are, thanks to certain markings.

"Do you think I care?" he grumbles, earning an eye roll from her.

"We might get lost," she hedges, tail flicking.

"Well, make sure we don't."

Sighing, she continues swimming along, knowing they're getting closer to their destination.

"Why are they nearer to upstate New York?" he questions with an undercurrent of annoyance.

"Less pollution," she answers curtly. "Your partner has tried to expand up here, no?"

"What my partner does is none of your concern, but yes, he has, without much success." He hums. "Ya know, I can't believe you guys don't have a power to give air or something. Aren't you known for saving sailors?" He adjusts his mask, the sound of his breathing surrounding her, giving off an eerie vibe.

She shrugs. "Well, we don't. You shouldn't believe everything you read." She tries not to laugh as they approach a cave.

"Is this it?" he asks in disbelief.

"A little further. The colonies aren't as apparent as Atlantis might be," she replies, entering the grotto, careful to make sure he's following along. She dives down a little farther before going straight.

"You sure this is the right spot?" His eyes narrow, gazing at her with suspicion.

"Yep." She forces her tone to be convincing as they continue and soon she stops at a darkened opening. "This way."

A malevolent smile spreads across his face as he swims past her eagerly into the small alcove, her following suit.

"So, where is it?" he demands, looking in every direction.

Acting fast, she gets on top of him, going for the tube connecting the air tank to the mask. They struggle, him trying to wrench her off. However, her arm strength is far superior, allowing her to grab him in a headlock, her right hand gripping the connection. She rips it out, completely detaching it from the mask and the tank. She throws it to bottom, the equipment forever lost to the abyss.

He staggers back, the lack of oxygen getting to him. She knows full well they're deep enough that he'll run out of air pretty quickly.

"Did you really think I would show you?" she hisses. "Let you kill my people?" She swims closer to him, glaring. "So, I'm going to ask you, is Bracken the one behind this? The one who's your partner? If you answer, I might let you live. Otherwise, you get to feel the way my partner did, only you won't survive." She knows it's wrong, but her body is boiling with anger, itching for revenge and craving justice.

She glowers, hovering over him. He's still struggling, gasping for air.

"Well?"

He nods fervently, a 'yes' barely escaping his lips.

Her lips curl in an almost sinister manner. "Good."

She swims behind him, wrapping her arm around his neck, rendering him unconscious, allowing her to bring them back to the surface.

When she resurfaces, she spots the location of the boat easily, due to the flares that illuminate the night sky. Quickly approaching, she yells for Castle.

"You got him?" he calls.

"Yeah," she answers holding up Alex's body and handing it off to Castle once she's close enough. She pulls herself up as Castle ties up their captor. Once he's finished, he turns his gaze toward her.

"You okay," he murmurs, cupping her cheek.

"I'm fine," she says with a grin. "Let's put him in the hull."

Making sure Alex is secure, Castle throws him in the space they were in hours ago. After closing the hatch, he places several oxygen tanks on it as well as other heavy pieces of equipment.

"That should keep him," Castle announces as Kate dries herself off. "So, now what? I don't think we have enough gas to get back."

Pursing her lips, she thinks. "You still have those flares?"

"Yeah." He cocks his head. "Guess we'll just light those up until someone comes."

The darkness allows the flares to burn bright, leaving Kate with the hope that the Coast Guard or someone will notice them.

It a takes a while, she's not sure how long, until she hears the whirl of a helicopter above them. They wave excitedly, attempting to get the attention of the pilot. The lights of a boat follow, announcing the arrival of the Coast Guard. The relief of the couple is palpable.

After some convincing, the authorities put a conscious Alex in cuffs and allow Castle and Kate onto the helicopter.

"I don't know about you, but I've had enough of small spaces for one day," Castle murmurs as she places her head on his shoulder. "Think I'm going to the loft for some sleep. Want to join me?"

"Just sleep?" she teases, raising an eyebrow.

"Why Detective, I never!" he gasps before kissing her forehead.

"I might entertain the idea," she answers, lacing her fingers with his. "But first, let's get you checked out and inform the boys and the captain that we're okay."

"Mmm hmm," he hums, beginning to nod off.

As they approach the city, she can feel herself start to doze, her eyes slowly closing, her body snuggling against her lover, her mind at peace.

They were finally safe.


	17. Chapter 17

AN: So, here's the next one! Thanks for all the follows, favorites, and reviews for this story! I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 17

A flurry of EMTs and police cars greet them when the couple comes down from the helicopter pad on top of a skyscraper. They're separated as soon as their feet hit the sidewalk, each dragged to another ambulance, objections leaving their lips as they part ways.

Rick grumbles as the medic pokes at him.

"Stay still," she scolds, checking his blood pressure.

"Sorry," he mumbles, casting a longing look toward the vehicle on the other end. Thankfully, he has a clear view of Beckett, who's looking his way. She tosses him a reassuring smile. Of course she's fine, but he still worries.

"You two are cute," the medic, Lily, says.

"Well, we were just in a life or death situation, so we're a little attached at the hip." He shrugs as a blanket is thrown across his shoulders.

"Besides a little hypothermia, you're fine," she says. "Now, go to her." She shoos him away, causing him to grin as he trots over to his partner.

"Everything check out okay?" he asks.

"Yep.," she answers, a mischievous twinkle in her eyes.

"Pretty much the same here, just a little cold." He sits next to her, giving her some of the blanket. She leans into him, sighing as he kisses her hair.

"Hey, guys!" a familiar voice calls out. Rick peers up to see Ryan and Esposito coming their way.

"Hey," the couple greets, not moving.

"Thank God you're okay!" Ryan exclaims. "We got the call about half hour ago that you guys got picked up. Took us a bit to get here."

"And you'll be happy to know that Alex is heading off to jail," Esposito chirps, grinning victoriously. "So, did he ever confess?"

Beckett nods. "Yeah, he admitted Bracken's behind all of this. We'll get him tomorrow."

"Uh uh," Ryan tsks. "Captain says you two are to be off tomorrow, no buts."

Rick isn't surprised at the little whine escaping Beckett's lips.

"Don't worry, we'll take care of the senator," Esposito assures her. "You'll get your chance with him."

"Thanks," she murmurs.

They two go to leave, but stop themselves.

"Hey, we gotta ask," Esposito starts. Beckett raises an eyebrow. "What was Alex talking about? The whole colonies thing? He seemed to think you knew what he was referring to?"

"He thought I was a mermaid," she answers, rolling her eyes.

"Where did he get that idea?" Ryan questions, furrowing his eyebrows.

"No idea." She lifts her shoulders in confusion.

"You? A mermaid?" Esposito cocks his head. "Still can't see it."

"Please," Castle scoffs. "She doesn't even believe in Santa." He hopes it adds an ounce of believability. Not that boys would ever seriously entertain the idea of her being a mythical creature.

She discreetly elbows him and he smirks.

"Well, night you guys. We'll keep in touch."

The couple waves as their colleagues walk off, still staying close to each other.

"Ready to go?" Rick asks, his lips next to her ear.

"Yeah."

They join hands, leave the ambulance, and walk to the street ahead.

He has a feeling they're going to be very cozy tonight.

* * *

When they enter the loft, she isn't sure what to expect. She's about to enter the home of a millionaire, something she never thought was going to happen, unless it was for a case.

When they step through the threshold, she's awestruck, though she tries not to show it. Her eyes scan the living room, taking in the tasteful decor. There's no bachelor pad feeling, which is nice.

"My mother may or not be home," he states, as if in warning. She's heard the stories of his vivacious mother, eager to meet her in person.

"Alexis, is that you, dear?" a voice calls from upstairs.

"No, Mother, it is your prodigal son," he calls out, snickering.

"Oh Richard. I thought you wouldn't be home for another few weeks." Her figure reaches the foot of the stairs, giving Kate a better view.

She dresses as lively as Castle has told. Her hair is bright red, much like the younger Castle's, from what Kate's seen from photos.

"Unfortunately, for you, no." He chuckles as he approaches his mother, kissing her on the cheek.

"And you must be Katherine," the matron states, blue eyes sparkling. "Richard has told me so much about you." She holds out her hand, which the detective takes. The older Castle's grip is friendly, welcoming, a knowing smile on her lips.

"I hope only good things, Mrs. Rodgers," Kate jokes.

"Only good things, and please, call me Martha," the red head assures. "So, what have you been up to, Darling?Still doing that case?"

"Yes and we just had a major break," Castle announces. "So, if you don't mind, we're going to head off to bed. We'll catch up in the morning."

Martha waves a hand dismissively. "Oh, okay, if you must be that way. Goodnight you two!"

He steers Kate to the hallway and then to what is presumably his office.

"Castle," Kate mumbles, looking around. She would observe more, but her exhaustion is getting the better of her. "What is your mother going to say about me being in your room for the first night?"

"That I am adult and can make my own decisions," he chirps. "Besides, she can't talk." There's no malice in his tone, only loving teasing. "So, I will give you some clothes to change into. Do you want to take a shower or something?"

She nods as they enter his bedroom. She didn't think she'd be in it so soon, but finds she doesn't mind one bit. It's cozy and the bed is definitely big enough for the two of them.

Rifling around in his dresser, Castle produces a set of clean clothes and gestures toward the bathroom. She beams, giving a peck on the lips as she grabs the pile and shuffles into the bathroom. Closing the door, she purses her lips, realizing the lack of a bathtub. Oh well, she'll just have to deal with it.

Hopefully, she fits.

* * *

Rick hums to himself, leaning against his headboard, scanning the messages on his phone. As he hears the water running, something dawns on him.

"Crap," he mutters, making his way to the bathroom. As he opens the door, he spots Beckett trying to adjust herself to the shower, her fin sticking out the door.

"I'm so sorry, Beckett," he apologizes. "I'll be right back." A few moments later, he returns, carrying a chair from the kitchen. "Here." He places it in the shower for her.

A gentle smile on her face, she grasps the chair, lifting herself onto it.

"I wish I could control it," she huffs. "You should see me when it rains. Sometimes I think I run faster those times than when chasing a perp."

He chuckles before his lips form into a pout. "Guess this means no shower or bathtub sex."

A loud laugh emanates from her as her eyes roll. "Unfortunately, no."

Dammit.

"Unless you want to feel me up."

"I can handle that."

She shakes her head, playfully throwing water at him. "Let me shower in peace. I'll be out in a few minutes."

He relents, striding back to his bed. To pass the time, he gives a quick call to Alexis, who says she's contemplating on coming home. While he encourages her to stay at the Hamptons, he doesn't keep the happiness out of voice at the prospect of being with his little girl again.

Soon, the bathroom door creaks open, prompting him to end the call, wishing his daughter good night.

"Was that Alexis?" Beckett asks, sliding into bed, her hair a beautiful mess.

"Yep, says she might be returning home soon," he responds, pulling the brunette to him.

"Do you think she'll like me?" Concern is clear in her voice.

"Like you? I think she already admires you." And he's sure Alexis will love Beckett, no doubt about it.

"I just don't want to interfere..."

"And you won't be," he insists, locking her gaze with his. "You'll fit right in."

"Mmm," she hums, uncertainty in her tone. He's not going to have it.

His hand goes to waist, pulling her firmly against him. His lips skim her earlobe, her cheek and land on her lips. His kiss is fierce, passionate, and soon his other hand tangles in her hair, hers doing the same. Soft moans leave her as his hand travels from her waist to her bottom, cupping her.

"As much as I would love to continue this," she states in between kisses. "I think we're both tired and I'd rather be wide awake when I have my wicked way with you."

He pulls away, scowling at her enticing smirk, knowing she's right.

"You're no fun," he grumps, laying down, gesturing for her to join him. She follows, snuggling up against him.

"I'm glad this case is almost over," she murmurs, head on his chest. "But it's forced me to realize that I shouldn't try to be so distant with the mermaid part of my life. Mom wouldn't have wanted that."

"I guess you'll just have to start things fresh with them then. What will happen with us?" Surely they wouldn't be allowed to remain together.

"I'll tell them we're a packaged deal," she responds. "Besides they know what would happen if we ever got separated or hurt. The consequences would be pretty severe."

"Is it something that would hurt you?"

She's quiet, clearly thinking something over. "Not as long as you're alive, I think. I mean I felt the effects of you being tortured." His body tenses, the mere thought of him being the cause of any of her pain horrifying him. She had told him before, but it's now really registering to him. Before he becomes lost in thought, her fingers trace circles on his stomach, soothing him. "My dad's alcoholism wasn't just a human reaction. Part of it was due to the fact that mermaids bond for life, and if one of them dies, it's almost unbearable for the other one to continue on."

"But your father was able to break free of that," he points out.

"Yeah, thankfully."

His lips ghost her forehead. "Well, you're stuck with me."

"How will I ever bear it?" she teases, peering up at him, her eyes full of joy.

"We'll find a way."

With that, he reaches over, flicking off the light.

"Goodnight, Kate."

"Night, Castle."

They drift off to sleep, both content to be in the others arms.


	18. Chapter 18

AN: Thanks for all the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 18

Rick wakes the next morning, a smile on his face as he nuzzles into the soft, warm body next to him.

"Morning," she husks, angling to face him

"Mmm, it's a very good morning," he croons.

"How are you feeling?" she asks, her fingers trailing along his bicep.

"Fine. Great actually," he chirps, giving her a quick kiss before waggling his eyebrows.

She laughs, peeling herself off of him. He scowls, reaching for her, but she shakes her head.

"I'm need to tend to my human side," she jokes, slipping into the bathroom.

Chuckling, he gets up, preparing himself for the day. As he does so, he can hear Kate moving around in the bathroom. It surprises and thrills him with how at ease they are together for the first time in his loft.

Soon, the door opens, revealing Kate in her clothes from the previous day.

"Espo just texted me," she states, holding up her phone. "They're bringing Bracken in now."

He sees the urgency on her face, the longing, knows she wants to be the one to break Bracken, and maybe she will. However, they need to give the boys a chance to warm up the senator.

"And he will be there tomorrow," he soothes. She huffs. "Come on and have some breakfast. My treat."

Her face bears a smile, but it doesn't quite reach her eyes. Guess he's found his goal for today: distract Beckett.

"So, what would you like? I have eggs, toast, pancakes, whatever you want." They go into the kitchen, and he begins to pull out pots.

"Um, scrambled eggs with bacon?"

"Coming right up!"

He cooks with skill and speed, showing off. Little oohs and ahhs, along with a few snickers, fall from his partner's lips.

"Here you go, m'lady." He pushes the plate in front of her and she begins to eat.

"This is delicious," she hums, scooping up more of the egg.

"You're totally welcome." He grins. "So, what do you want to do? I have a vast collection of DVDs. We could stream something. Oooh, how about laser tag?"

"Castle!" She rolls her eyes, her expression amused. "A movie is fine with me."

As she goes to pick one out, he prepares snacks. Nothing too crazy, since they just ate. After a few minutes, he comes into the living room holding a bowl of popcorn and pretzels.

"So, what are we watching?"

She shows three movies and he beams.

"A trilogy, huh?"

"I figured they'd be a good distraction." She shoots him a knowing look, and he sits next to her, unperturbed.

"Okay then, let's get started."

Before starting the film, they shut off their phones in order to avoid any temptation. They curl up next to each other, both reaching for the popcorn.

They watch, neither moving. Time passes and Rick finds himself completely forgetting about the case. He's not sure it's the same for Beckett.

Glancing down, he observes her. She's staring at the screen, seemingly relaxed, no traces of anxiety or stress on her face. He thinks this is the most calm he's seen her the past few days.

She peers up at him, raising an eyebrow as the credits roll on the screen.

"Staring is creepy," she teases, getting up from the couch. He sees her hand go for the phone, but she restrains herself.

"Do it, just in case they sent something."

She nods, quickly turning on the phone. Waiting a beat, seeing nothing, she goes to turn it off. Unfortunately, it dings as her finger hovers over the power button. She purses her lips, eyes scanning the text.

"What's up?"

"They haven't gotten far..."

"Because?"

"He only wants to talk to the lead detective," she grouses, running a hand through her hair.

"Well, we knew he wasn't going to make it easy." A man of Bracken's caliber was not going to go down without a fight. "Do you want to go in?" He wouldn't blame her if she does.

She gnaws at her bottom lip, reading the message over. She's quiet, contemplative. Finally, resolve reaches her eyes. She texts something, and to his surprise, powers off the device.

"With all the things he's done, sitting in holding for a bit won't kill him, or me," she says, plopping down next to Rick.

He smiles, glad to see her thinking clearly.

So, he flips on the next movie and she returns to her position up against him.

They enjoy the rest of the afternoon without any disturbances.

* * *

Evening falls just as the couple finishes their movie marathon.

"Hmm, I'm glad I did that," Kate murmurs, stretching. It's true. It was nice to relax for once instead of having to go into the precinct.

"I'm glad you're glad," Castle responds with a grin. He rises from the couch before heading for the kitchen. "What would you like for dinner?"

She sighs, wishing she could stay. However, she needs to clean herself up and change her clothes.

"I'm actually going to head home, freshen myself up," she says. "Plus, I need to get my head into the game for tomorrow."

He raises an eyebrow, smirking. "Are you saying I'm a distraction, Detective?"

Rolling her eyes, she strides toward him, chest to chest, wrapping her arms around his neck.

"Yes, I most certainly am. A very good distraction." She places a chaste kiss on his lips. "But not right now." She's needs to focus, and right now, being alone is the only thing that will help keep her on track.

He pouts, but apparently accepts her explanation as he kisses her.

"See you tomorrow?" he murmurs.

"Tomorrow." She nods before leaving the left, her heart already feeling heavy as she closes the door.

When she arrives home, she's not much better. She knows part of it is because of the whole soulmate thing, but another part is because she's truly does have feelings for Castle and enjoys his companionship. She's never been a clingy person, but Castle invokes something in her, something that she's never felt for anyone.

She prepares for bed, slightly regretting that she didn't stay the night at Castle's loft. Her lips turn up in a mischievous smile, knowing what they probably would have done if she'd spent the night.

She goes to sleep, knowing that the case is almost over.

When she arrives at the precinct the next morning, she's not surprised to see Castle sitting at her desk. Espo approaches her, saying Bracken's in interrogation. Walking up to her partner, she forces out a smile, slightly nervous.

"You ready?"

"Whenever you are."

They walk into observation, staring at the man who's ruined multiple lives for the sake of immortality, sitting as calm as can be. The fury bubbles inside her, the urge for justice growing stronger than ever. As the emotions swirl, a calming hand touches her shoulder.

"You've got this," he murmurs.

Gazing at him, she feels the admiration and assurance waving off of him. Nodding, she grips the doorknob.

"Let's finish this once and for all," she states. They walk into the room, and sit down, facing the senator, who wears a smug smile across his face. She knows it won't be a walk in the park, but she has her partner beside her. They'll close this case.

Together.


	19. Chapter 19

AN: Here's the next one! Thanks for all of the follows, favorites, and reviews for this story. I really appreciate them!

Disclaimer: I don't own Castle.

* * *

Chapter 19

Rick watches as Beckett sits, exuding confidence as she begins her questioning.

"Senator Bracken, I'm Detective Beckett and this is my partner Richard Castle," she starts, opening the file in front of her.

"The novelist?" The senator raises a surprised eyebrow, but Rick's sure the man is anything but.

"I heard you gave my colleagues a hard time with their questions, that you wanted to talk to me," she continues, lips forming into a thin line.

"Well, I feel that a person of your caliber would understand the silliness of these allegations," Bracken replies. "I mean, me commit murder? Please." He shakes his head. "Why would I do such a thing? You must realize how much I contribute to the community."

Neither Rick nor Beckett are moved by the politician's speech.

"Speaking of contributing to the community, you seem to be gunning for the expansion of diving areas around New York. Why is that?" Rick quizzes.

"Well, I want everyone to experience the beauty of New York. What's wrong with that?"

"Because that's not it, is it? Your partner Alex signed an affidavit stating that you and him went around to a few diving instructors throughout the city. We also interviewed a diving instructor, she said Alex was with a partner who kept asking about mythology and various diving spots in the city. Alex confirms it was you."

Rick knows Beckett's lying through her teeth about the first part, but whatever will get Bracken to talk, she needs to do it.

"Look, Detective, I don't know who this Alex person is, but you've clearly got the wrong guy." Bracken starts to rise from his seat, but the detective's stare stops him cold.

"Sit down, Senator," she hisses. "Alex has confirmed to us that you're his partner in this. So, why don't you make it easy? You've been looking to expand because you think you'll be able to find the colonies that way. You killed those girls because you thought they were mermaids and could give you immortality. How did you get it done? You two alternate with luring the girls in?"

Rick jumps in, assessing the senator. "No, you didn't. You did the luring. You're a politician, so you're able to adapt yourself to what people want, what they need. Alex was the one who did all the dirty work, right? Killed the girls and brought you back their blood."

He can see the absolute fury on Bracken's face, his cool mask slowly slipping.

"You two are insane," he snaps. "I have no right to be held under this kind of nonsensical questioning."

"If we are, why are you not answering?" Beckett smirks.

"I believe Detective Beckett has a point," Rick snarks.

Bracken narrows his eyes, examining the female detective.

"Beckett," he murmurs, thinking. A second later, his eyes light up as he realizes something. "You're Johanna Beckett's daughter, aren't you? Little Katie Beckett all grown up." He huffs. "Your mother never was fond of me. Unfortunately, it seems that attitude has rubbed off on you."

Rick glances over to his partner, seeing her struggle with maintaining her composure.

"What my mother thought of you or lack thereof isn't this issue here," she snaps. "The issue here is that you're being accused as an accomplice to murder and not answering our questions." She leans forward, her voice dropping a tone, ice like. "So, let's keep our focus here, okay?"

Bracken glares, pursing his lips.

"I bet if we go through your computer and phone we'll find files of pictures that you sent the girls." Her tone has changed, turning into a low, soothing murmur. Rick knows what she's doing, but will it work? "All the places you and Alex supposedly went, just to make them think they had someone they could trust. I mean I get it. Who wouldn't want everlasting life?" She smiles, her voice becoming more hypnotizing by the minute. "All the things you could do, the promises you could fulfill, with an unlimited life span. Sounds like a good deal to me." If Rick could applaud, he would. Her interrogation skills and story building never cease to amaze him.

Meanwhile, several emotions flicker across Bracken's face: lust, annoyance, indigence, and finally, understanding.

"You're one of them," he murmurs, lost in her hypnotism.

"Huh?" Beckett asks, furrowing her eyebrows in confusion.

"You're one of them," he repeats, louder this time.

"One of who, Senator?"

"Don't play dumb," he snips.

"I assure you I don't know what you're talking about," she responds cooly.

However, Bracken is wild, turning his attention toward Rick. "You see what she's trying to do, don't you? Trying to hypnotize me." He shakes his head. "Alex told me you had the birthmark but I didn't you'd actually be-" The politician stops himself, the consequences of his words dawning on him.

"Guess we can confirm your partnership with Alex." A cheshire cat like grin forms on Beckett's face and Rick restrains the urge to do a fist pump.

"You little-You tricked me!" Bracken shouts.

"I did no such thing," Beckett spits. "Come on, Senator, let's finish this up." She adjusts her position, as if preparing to strike. "You lured the girls and got them to trust you and then had Alex kill them on the full moon. You two split the blood, I'm betting. We've seen the pictures, you haven't aged a day.""You can't prove anything," he starts, seeing how he's lost control of the room.

"You know things, Senator, things you can't find in a regular book. Information no other human would know unless they've done the real research or have had firsthand experience."

"And you've had some personal experiences haven't you?" Rick adds, his adrenaline building. "There's no way you would've orchestrated all of this without having first hand knowledge. So who or what did you see that convinced you so much that this could be possible?"

Bracken grits his teeth and clenches his fists.

"About twenty five years ago, I was fishing upstate with a few friends. We went out into the river, in our usual spot. It was cloudy out, pretty much going to thunderstorm anytime. However, being the young, stupid people we were at the time, we stayed in the water." He shakes his head. "Soon, a thunderstorm came, making the waters rough. We were in different boats and tried to return to shore. However, the waves were strong and my boat turned over. I struggled to swim to shore, I thought I was going to drown." His lips lift into a small smile. "But someone saved me. I thought I was hallucinating at first, but it turns out a woman, who had a green fin, rescued me."

"What made you realize you weren't having delusions?" Rick inquires.

Bracken shrugs. "She came back to check on me and I caught her."

From his peripheral vision, the author notices his partner raise an eyebrow.

"We…bonded and she told me things, many things." Bracken smirks. "I was just about able to keep the lust at bay. However, one night, during a full moon actually, she told me she had fallen for me." He releases a sigh of dismay. "I informed her I didn't feel the same. She was distraught, apparently. Very Hans Christian Anderson." He hums, going on. Rick's skin crawls, seeing how much of a soulless monster the man is, if he can even be considered human. "Killed herself a few minutes later by driving a sea urchin into her stomach. I didn't realize that the poison could act so quickly." He waves his hand dismissively. "Anyway, I remembered what she'd told me about mermaids and the full moon, so I utilized her blood. The effects were instantaneous. But unfortunately, it's so hard to find mermaids nowadays," he sneers, looking the brunette up and down.

"You broke her trust," Beckett hisses.

"Yeah, but I still gained something from it." He rolls his eyes. "Anyway, it's not like anyone's going to believe that story. Mermaids? What jury or judge would believe that?"

"We still have probably cause," Rick points out. "And Alex's corroboration. So, they can make a decision based on that."

"Please, they wouldn't put a highly influential senator behind bars." He scoffs. "Besides, a senator taking the time to go through a website to look for mermaids? No way."

Bingo!

Beckett cocks her head. "I never told you what you used to lure the girls in and I know my colleagues didn't either. Also, the NYPD never released that information." Her tone carries an undercurrent of conviction. Rick can practically taste victory.

All the blood drains from Bracken's face at the detective's statement. "Well, you referred to my computer, so one can only assume…" he trails off, unsure of what to say.

Standing up, Beckett unhooks her cuffs from her belt. "Stand up." The senior reluctantly complies. "William Bracken, you're under arrest for accomplice in murder as well as aiding in kidnapping members of the NYPD." She reads him the rest of his rights, before walking him to holding. Her stride is triumphant, along with Rick's. The sound of the cell door slamming is music to his ears.

"Way to go you guys!" Ryan cheers from the middle of the bullpen, having come from the observation room.

"Yeah, you even had us going for a bit. Making him believe that you were a mermaid, nice," Esposito says.

Captain Montgomery joins them. "Congratulations, you two finally caught the Full-Moon Killer or rather, killers." He grins, but his expression sobers. "There's going to be hell for this. You don't arrest a senator without ruffling some feathers."

"Of course, Sir," Beckett answers, her eyes reflecting understanding. "We'll deal with it as it comes."

"Right." Looking at all of them, the captain waves his hand. "Now, all of you get out of here and celebrate. Have a drink on me since I'll be fielding phone calls shortly. I expect you here bright and early tomorrow."

A chorus of 'thank you' emanates from the group before heading out. When they enter the elevator, Beckett doesn't hesitate as she grasps Rick's hand, earning a smile from him. She winks.

"Aww," Ryan says.

"You two are going to be all cute and mushy since we finished the case, aren't you?" Esposito gripes teasingly.

"Yep," Rick answers. "Will it help if drinks are on me?"

"Mmm, maybe," Espo remarks, snickering.

The group steps off the lift, ready to celebrate. Rick looks beside him at the friends he's made over the past few weeks.

He definitely feels like part of the team.

* * *

They drink and make merry at the bar, all feeling victorious at the closing of their case.

"So, how long have you two, ya know," Ryan gestures between the two as Kate rolls her eyes.

"Just a couple of weeks, really."

"But something's been there since the beginning," Castle chirps.

"Beginning?" Esposito lets out a disgusted noise. "You've only been with us for about a month."

Castle shrugs. "The heart wants what the heart wants." He places his hand over hers, and she grins. If they weren't soulmates, she'd think he was giving them a line.

"And you guys know me. He's out the door if he hurts me." She knows that's the last thing he would do, though.

"What she said," Castle chimes, finishing his beer.

"Well, it's sweet," Ryan says, nursing his cocktail.

Castle checks the time on his phone. "I think I'm going head out you guys."

"Mmm, me too," Kate remarks, finishing her shot. She's warm, but not tipsy. "I'll follow you out."

"And home," Espo snarks, sipping his own drink.

Kate sticks her tongue out at him before trailing behind Castle.

"Escorting me home, Detective?" he teases, wrapping an arm around her waist.

"Yep." She pops the 'p', leaning into him.

"I should pay you for your services, but I don't know how."

"Oh, I'm sure we can come up with something," she states, her tone enticing.

"I've been told I have a great imagination." He snickers.

The chuckle in unison, teasing each other with innuendos the rest of way.

When they reach the loft elevator, the heat between them is palpable with the promise of what's to come. She just about able to restrain herself as they travel up to his floor. The practically run to the loft door, Castle opening the door as quick as he can.

The moment they cross the threshold, their hands are on each other, exploring, searching.

"Your mother?" she asks half heartedly, tugging at the hem of his shirt.

"Out," he murmurs, hands pushing up her shirt.

She kisses him, fierce, passionate. He responds in kind as one hand unbuttons her blouse.

"Bedroom, now," she growls in-between kisses. Wrapping her legs around his waist, she allows him to carry her to the room, his kisses trailing down her neck, to her shoulder blades, and finally to the middle of her breasts. Each kiss feels glorious, adding to heat already running through her veins.

He gently places her on the bed before continuing the exploration with his lips. When he reaches her stomach, he unbuttons her pants and slides them down. She moans, feeling his hot breath near her navel.

"You're overdressed," she purrs, forcing him up by the shoulders. She practically rips off his shirt and unzips his jeans, pulling them down to his ankles before he steps out of them.

"Eager one, aren't you?" he teases, standing in front of her with his shirt open, exposing his bare slightly muscular, chest, his black, cotton boxers the only barrier to what they both desire.

"Yes. Now come here and make love to me," she murmurs, arms outstretched.

He grins, covering her body with his, enveloping her in his arms.

"I love you so much, Kate Beckett," he whispers in ear.

He spends the rest of the night proving it.

And so does she.


	20. Chapter 20

AN: Note at the bottom.

Disclaimer: I don't own Castle.

* * *

Chapter 20

A few days later, Rick instructs two burly men where to place the brand new bathtub he'd ordered the previous day.

"That's perfect," he praises. "Will it take long to install?"

"Nope, and the spot is actually good to hook it up to the water source," James, the younger of the two men, replies.

"Fantastic!" Rick grins, making a mental note to tip the two workers nicely before they leave.

He allows them to work, wandering into the kitchen. As he does so, the lock to the front door clicks before opening, revealing a very excited and out of breath Alexis.

"Hey, Dad!" she greets, rolling her suitcase into the foyer.

"Hello, Pumpkin." He hugs her tight, kissing her fiery red hair, happy to have his little girl back home. "How was the Hamptons?"

She shrugs. "Okay, as I told you. I think I would've preferred it more if you were there."

He chuckles. "Look at you, buttering me up."

Smirking, she grabs her bag. "You love it. Anyway, I'm gonna unpack. Be down in a bit."

As she bounds up the stairs, he pulls out some graham crackers, chocolate, and marshmallows from the cabinet. No better welcome home than devouring s'mores. Speaking of, he doesn't believe Beckett has had the pleasure of eating one of his delicacies. Well, that will change.

Just as he arranges the marshmallows on a pan, a loud scream arises from upstairs, Alexis' room to be exact.

Rick immediately drops the tray, heart pounding as he runs up the stairs, throwing open the door to his daughter's room.

"Alexis!" He rounds the corner to the small entryway that goes into her bathroom.

The image in front of him raises alarm bells in his head. Alexis' back is up against the door of the bathroom, eyes wild with confusion and fear. When she spots him, she sprints toward and slinks behind his form.

"What's the problem?"

"There's a giant fish or something in the tub," she explains, her voice quivering.

Giant fish?

Oh.

Oh crap!

He'd forgotten he'd told Beckett to use one of the upstairs bathrooms since his mother and Alexis both have a tub. Guess he knows which one she chose.

"Uh, hold on a second." He goes to the door, but Alexis stops him.

"What are you doing?" she hisses, gripping his arm, horror written on her face.

"Just give me a minute," he pleads. She purses her lips, releasing him.

Cracking the door open, he notices Beckett attempting to hide her fin. Realizing it's him, she shoots him an apologetic glance.

"Sorry," she murmurs. "I was just about to come out."

He waves a dismissive hand, the other throwing her a towel.

"Don't worry about it," he says. "But, uh, I assume we should tell her? Otherwise it's going to be really hard to craft a story of me wrestling a fish."

"I mean, we kind of wrestled earlier." She leers, as he tries to not think about the delicious things they did earlier that morning. "But yeah, it's fine. Just let me dry off."

Nodding, he opens the door, immediately shutting it once he's on the other side.

"What's going on?" Alexis inquires.

"Everything will be explained in a bit," he placates, grabbing her hand and escorting her out of the room.

"But-"

He sighs, shaking his head. "You're just going to have to wait, okay?"

She scowls, clearly not pleased, but nods anyway.

As they wait, he toasts the marshmallows and assembles the dessert, the smell of the chocolate and marshmallows causing him to grin. He wonders if Beckett can smell it.

"Something smells delicious," a voice pipes from the stairs. Speak of the devil.

Both Rick and Alexis turn to watch the brunette make her way down the steps. Her hair is still wet, but gorgeous, of course.

Alexis furrows her eyebrows in confusion, glancing between the two.

"Alexis, meet Kate Beckett," he says, walking over to his partner, grasping her hand, guiding her to the island.

"The detective you've been following?"

"The very same," he answers.

"Uh, wow," Alexis murmurs. She isn't mad, just very surprised.

"I'm, uh, sorry for scaring you. Your dad said you wouldn't be back until tonight." A nervous chuckle escapes the detective's lips.

"Scaring me? Oh." Alexis rolls her eyes. "Did Dad talk you into pranking me?" She glares at her father. "Where did you get the fin?" Silence. "Come on, where'd you get it? It looked so real." More silence. "What?"

Beckett clears her throat. "Alexis, your father didn't buy the fin. It's mine."

"Oh, so you bought it?" The red head furrows her eyebrows in confusion.

"No...I mean it's mine, mine." She gnaws at her lip, rocking back and forth on her heels.

"Yours-Oh!" Finally, it dawns in her. "Oh my god, really?" Her eyes flicker to her father, who nods in response.

"Told you she was extraordinary," he chimes, wrapping an arm around Beckett.

"So, you're really a-"

"Mermaid? Yeah." He notices his partner relax, a soft snicker escaping her. "I'll answer any questions you have while we consume the s'mores your father made."

The teenager nods, eagerly grabbing a plate.

As the trio eats, Alexis quizzes the detective, asking many of the same questions he did. She's calm and understanding as Beckett explains different aspects of her life along with what is true and what isn't when it comes to mermaid mythology.

"This is so cool!" the teenager exclaims once she finishes her interrogation.

Beckett lets out a loud laugh. "You are your father's daughter."

"And obviously you guys are together." Alexis hums. "You guys are pretty cute, it's so obvious."

"I'm glad to have your approval," Beckett answers sincerely.

At that moment, the two men who'd been working on the tub reappear. Rick thanks them, giving them both a hefty tip as he shakes their hands.

"What were they doing in there?" Beckett asks.

"Installing a tub."

"You didn't." Her expression turns to disbelief, her jaw dropping.

"Oh but I did. I do like sharing my bathroom with you, Beckett. Besides, the tub is very spacious." He winks as Alexis groans.

"Didn't need to hear that."

"Sorry, Pumpkin," he sing songs as Beckett hides her face in his neck.

"So, are you going to tell Gram?"

"Er, at some point, whenever she comes home." He sighs, knowing his mother's flair for the dramatic will impact her response. However, he's sure she'll be okay with it.

"Okay, well, I'm going to make sure I haven't gotten any assignments yet." His daughter hops off the stool. "Thanks for the food, Dad." She kisses him on the cheek before giving Beckett a small wave. "Welcome to the family, Kate."

The red head heads up to her room, the couple remaining at the counter.

"Hear that?" He beams. "You're part of the family."

"I see," she hums. "I'm glad she likes me."

He scoffs. "Please, what's not to like?" That earns him a snort. "Anyway, want to check out the new tub?"

Narrowing her eyes, she shakes her head, her lips turning up in a playful manner. "Okay, but check out does not equal use."

"Got it."

When they enter the bathroom, she oooos and ahhs over the new piece of porcelain. It's a simple, yet elegant, white tub with golden claw feet and spout. The container is big enough for the both of them.

As she examines it, he finds his imagination getting away from him. Visions of a little girl with Beckett's hair splashing and playing in the water as one of them bathes her runs through his head. Another one, this time with Beckett in the tub as their child plays with her fin, crosses his mind.

"What are you thinking about?"

"Mmm, nothing," he answers. He'll tell her another time. "So, what time do you need to be in?" With the closing of the case, the captain has been lenient about when the team needs to come in for the next few days.

"I better go now, actually. Poor Montgomery has been keeping the press at bay for the past several days. Time for me and the boys to chip in."

He nods, scratching his head. "Yeah, the mayor called me yesterday, having obviously caught wind of the situation. I haven't returned his call." Rick is so not looking forward to having to explain to his closest friend how the senator is the one behind all of the murders.

"So, it looks like we both have work to do. Come on then." She grins, sashaying out of the room.

He chuckles softly, following after her before coming in step, linking her fingers with his. She smiles, squeezing his fingers, her eyes reflecting love and trust, knowing they are partners.

And always will be.

 _The End_.

* * *

AN: There it is folks! Thank you so much for joining me on this journey. I really appreciate those who stuck with me, whether you have been with me since the beginning or are just reading now. All the support for this story has astounded me, particularly since this was such a strange idea. So, I sincerely thank everyone for their constant cheerleading.

Another thing, if you follow me on Twitter, you are most likely very aware that I start law school this week. Due to this, I will be studying a lot and unfortunately, that means little to no writing will be done. So, as of now, this story is my last multi chapter. I might be posting one shots on occasion when I can, but this will be my final multi chapter fic.

See you around!


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